feat(scep): SCEP probe in network scanner for fleet-readiness assessment

Phase 11.5 of the SCEP RFC 8894 + Intune master bundle. Adds an
operator-facing SCEP probe that issues GetCACaps + GetCACert against
an arbitrary SCEP server URL and returns a structured posture snapshot
(reachable + advertised caps + RFC 8894 / AES / POST / Renewal /
SHA-256 / SHA-512 support flags + CA cert subject + issuer + NotBefore
+ NotAfter + days-to-expiry + algorithm + chain length).

Two operator use cases per the master prompt:

  1. Pre-migration assessment — probe an existing EJBCA / NDES SCEP
     server before switching to certctl to see what capabilities it
     advertises and what the CA cert looks like.
  2. Compliance posture audits — periodic ad-hoc probes against the
     operator's own SCEP servers to flag drift.

Capability-only — does NOT POST a CSR per the spec (would consume slot
allocations on the target server + create audit noise). Standalone CLI
binary explicitly out of scope (per the master prompt §11.5.6 and the
operator's confirmation): the probe code lands inside certctl; a
future thin Cobra wrapper is a separate decision.

Backend (six new + one extended file):

  * internal/domain/network_scan.go — new SCEPProbeResult struct with
    every probe field documented for the GUI's display layer.

  * migrations/000021_scep_probe_results.up.sql + .down.sql — new
    scep_probe_results table with TEXT id, target_url, all probe
    flags, CA cert metadata, probed_at, probe_duration_ms, error.
    Two indexes: idx_scep_probe_results_probed_at (DESC) for the
    'recent probes' GUI query, idx_scep_probe_results_target_url
    (target_url, probed_at DESC) for the future per-URL history view.

  * internal/repository/interfaces.go — new SCEPProbeResultRepository
    interface (Insert + ListRecent).

  * internal/repository/postgres/scep_probe_results.go — Postgres
    implementation. ListRecent clamps limit to [1, 200]; on read
    re-derives ca_cert_days_to_expiry against the query-time wall
    clock so 'X days remaining' stays fresh.

  * internal/service/scep_probe.go — ProbeSCEP(ctx, url) on
    NetworkScanService. Validation order:
      1. Up-front URL validation via validation.ValidateSafeURL
         (defaults to validation.ValidateSafeURL but injectable for
         tests via the new scepValidateURL field on the service).
      2. Dial-time SSRF re-check via SafeHTTPDialContext on the
         http.Transport (defends against DNS rebinding).
      3. GET ?operation=GetCACaps + GET ?operation=GetCACert.
         GetCACert handles three response shapes: PKCS#7 SignedData
         certs-only envelope (multi-cert), raw DER (single-cert),
         and PEM-wrapped DER (non-conforming servers).
    Times out at 30s; uses a 1MB body cap for DoS defense; wraps
    the result + persists via the repo (nil-safe) before returning.
    describeCertAlgorithm helper returns 'RSA-N' / 'ECDSA-curve' /
    'Ed25519' / 'DSA' for the GUI's algorithm column.

  * internal/service/network_scan.go — added scepProbeRepo +
    scepHTTPClient + scepValidateURL + scepIDFn + nowFn fields;
    SetSCEPProbeRepo wires the repo at startup.

  * internal/api/handler/network_scan.go — extended NetworkScanService
    interface with ProbeSCEP + ListRecentSCEPProbes; added two new
    HTTP handlers:
      POST /api/v1/network-scan/scep-probe   (body {url})
      GET  /api/v1/network-scan/scep-probes  (recent history)
    Synchronous probe; HTTP 200 with the result body for both success
    and reachable-but-failed cases (so the GUI can render the failure
    tone with the operator-actionable error message).

  * internal/api/router/router.go — registered the two routes inline
    after the existing network-scan target endpoints.

  * api/openapi.yaml — documented both endpoints (operationId
    probeSCEP + listSCEPProbes) with full schema + response codes.

  * cmd/server/main.go — wires the new SCEPProbeResultRepository
    onto the network scan service via SetSCEPProbeRepo right after
    the existing NewNetworkScanService construction.

Backend tests (6 new — exit-criteria-named per the master prompt):

  * TestProbeSCEP_AdvertisesAllCaps — happy path, full RFC 8894
    capability set, ECDSA P-256 CA cert, 365-day expiry.
  * TestProbeSCEP_MissingSCEPStandard — pre-RFC-8894 server (only
    POSTPKIOperation + SHA-1 + DES3); SupportsRFC8894 = false.
  * TestProbeSCEP_GetCACertExpired — CA cert NotAfter 30d in the
    past; CACertExpired = true.
  * TestProbeSCEP_Unreachable — connect to TCP port 1; probe
    returns Reachable=false + non-empty Error.
  * TestProbeSCEP_RejectsReservedIP — http://169.254.169.254/scep
    (EC2 metadata literal) rejected by the up-front
    validation.ValidateSafeURL gate; result captures the error
    without ever issuing the HTTP call.
  * TestProbeSCEP_PEMWrappedCert — server returns PEM instead of
    raw DER for GetCACert; the fallback parse path handles it.

Frontend (one extended file + types/client):

  * web/src/api/types.ts — SCEPProbeResult + SCEPProbesResponse.
  * web/src/api/client.ts — probeSCEPServer + listSCEPProbes
    helpers.
  * web/src/pages/NetworkScanPage.tsx — new SCEPProbeSection
    component + ProbeResultPanel (with capability badges + CA cert
    details panel + raw caps line) + SCEPProbeHistoryTable. Form
    rejects empty URL with inline error before calling the API.
    Reload mutation goes through useTrackedMutation with explicit
    invalidates: [['scep-probes']] (M-009 contract).

Frontend tests (5 new + 0 regressions):

  * Scep probe section header + form renders.
  * Empty URL is rejected with inline error and never calls the
    probe endpoint.
  * Successful probe renders capability badges + CA cert subject
    + days-remaining inline panel.
  * Probe-level errors are surfaced in the inline panel (no result
    panel rendered).
  * Recent-probes history table renders one row per probe.
  * (Existing 2 NetworkScanPage XSS-hardening tests stub the new
    listSCEPProbes endpoint to an empty list so they still pass.)

Verification:
  * gofmt clean on touched files
  * go vet ./... clean
  * staticcheck on service+handler+router+repository+cmd-server clean
  * go test -short across service+handler+router+repository+cmd-server
    + integration: all green (existing + 6 new probe tests pass)
  * Frontend tsc --noEmit clean
  * Vitest: 7/7 NetworkScanPage tests pass (2 existing XSS + 5 new
    probe section)
  * G-3 docs-drift CI guard reproduced locally clean (no new env vars)
  * M-009 hard-zero useMutation guard clean (probe mutation goes
    through useTrackedMutation)
  * openapi-parity guard satisfied (both new routes documented)
  * The mockNetworkScanService in handler + integration packages
    extended with stub Probe methods; targeted coverage stays in
    scep_probe_test.go.

Out of scope (per master prompt §11.5.6 + operator confirmation):
  * Standalone certctl-scan CLI binary — separate decision, ~1d of
    follow-up work when/if shipped.

Refs: cowork/scep-rfc8894-intune-master-prompt.md::Phase 11.5
      cowork/scep-rfc8894-intune/progress.md

api/openapi.yaml

@@ -732,6 +732,109 @@ paths:
         "500":
           $ref: "#/components/responses/InternalError"
 
+  /api/v1/network-scan/scep-probe:
+    post:
+      tags: [SCEP]
+      summary: Probe an SCEP server for capability + posture
+      description: |
+        Synchronous probe against an SCEP server URL. Issues
+        `GET ?operation=GetCACaps` and `GET ?operation=GetCACert`
+        and returns the structured `SCEPProbeResult` (reachable,
+        advertised caps, RFC 8894 / AES / POST / Renewal / SHA-256 /
+        SHA-512 support flags, CA cert subject + issuer + NotBefore +
+        NotAfter + days-to-expiry + algorithm + chain length).
+
+        Capability-only — does NOT POST a CSR (would consume slot
+        allocations on the target server + create audit noise). Used
+        for pre-migration assessment + compliance posture audits.
+
+        SSRF-defended: the URL is validated up-front (reserved IPs
+        rejected) AND the underlying HTTP client uses the
+        SafeHTTPDialContext that re-resolves the host at dial time
+        (defends against DNS rebinding).
+
+        Result is persisted to the `scep_probe_results` table via
+        migration 000021 so the GUI can show recent probe history.
+        SCEP RFC 8894 + Intune master bundle Phase 11.5.
+      operationId: probeSCEP
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              type: object
+              required: [url]
+              properties:
+                url:
+                  type: string
+                  format: uri
+                  description: Base SCEP server URL (no `?operation=...` suffix needed; the probe appends its own operations).
+      responses:
+        "200":
+          description: Probe completed (the result body's `error` field carries any sub-step failure)
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  id:
+                    type: string
+                  target_url:
+                    type: string
+                  reachable:
+                    type: boolean
+                  advertised_caps:
+                    type: array
+                    items: { type: string }
+                  supports_rfc8894: { type: boolean }
+                  supports_aes: { type: boolean }
+                  supports_post_operation: { type: boolean }
+                  supports_renewal: { type: boolean }
+                  supports_sha256: { type: boolean }
+                  supports_sha512: { type: boolean }
+                  ca_cert_subject: { type: string }
+                  ca_cert_issuer: { type: string }
+                  ca_cert_not_before: { type: string, format: date-time }
+                  ca_cert_not_after: { type: string, format: date-time }
+                  ca_cert_expired: { type: boolean }
+                  ca_cert_days_to_expiry: { type: integer }
+                  ca_cert_algorithm: { type: string }
+                  ca_cert_chain_length: { type: integer }
+                  probed_at: { type: string, format: date-time }
+                  probe_duration_ms: { type: integer }
+                  error: { type: string }
+        "400":
+          description: Missing or malformed `url` field
+        "500":
+          $ref: "#/components/responses/InternalError"
+
+  /api/v1/network-scan/scep-probes:
+    get:
+      tags: [SCEP]
+      summary: List recent SCEP probe results
+      description: |
+        Returns the most recent 50 SCEP probe results across any
+        target URL, ordered by `probed_at` descending. Backs the
+        GUI's "Recent SCEP probes" history table on the Network
+        Scan page. SCEP RFC 8894 + Intune master bundle Phase 11.5.
+      operationId: listSCEPProbes
+      responses:
+        "200":
+          description: Recent probe results
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  probes:
+                    type: array
+                    items:
+                      type: object
+                  probe_count:
+                    type: integer
+        "500":
+          $ref: "#/components/responses/InternalError"
+
   /api/v1/admin/scep/profiles:
     get:
       tags: [SCEP]