feat: add frontend action buttons, fix notification auth bug, add 53 Vitest tests

Bug fix:
- markNotificationRead was using raw fetch() without auth headers,
  bypassing the shared client's Authorization header. Moved to
  api/client.ts to use fetchJSON with proper auth.

New action buttons:
- CertificatesPage: "New Certificate" modal with form fields
- CertificateDetailPage: "Deploy" button with target selector modal,
  "Archive" button with confirmation
- IssuersPage: "Test Connection" and "Delete" per-row actions
- TargetsPage: "Delete" per-row action
- PoliciesPage: "Enable/Disable" toggle and "Delete" per-row actions

New API client functions:
- updateCertificate, archiveCertificate, registerAgent,
  createPolicy, updatePolicy, deletePolicy, getPolicyViolations,
  createIssuer, testIssuerConnection, deleteIssuer,
  createTarget, deleteTarget, markNotificationRead

Frontend tests (53 tests, 2 files):
- client.test.ts: 35 tests covering all API endpoints, auth headers,
  401 handling, error parsing, HTTP methods, request bodies
- utils.test.ts: 18 tests covering formatDate, formatDateTime,
  timeAgo, daysUntil, expiryColor

CI: Added "Run Frontend Tests" step to frontend-build job

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/tsconfig.json

@@ -15,7 +15,8 @@
     "noUnusedLocals": false,
     "noUnusedParameters": false,
     "noFallthroughCasesInSwitch": true,
-    "forceConsistentCasingInFileNames": true
+    "forceConsistentCasingInFileNames": true,
+    "types": ["vitest/globals"]
   },
   "include": ["src"]
 }