feat: read-only FHIR R4 server (share records over /fhir)

Expose temetro's own records as a read-only FHIR R4 server at /fhir,
authenticated with per-clinic API keys (tmf_… bearer tokens, SHA-256
hashed, shown once). Serves Patient, Observation (labs + vitals),
AllergyIntolerance, Condition, MedicationRequest, Encounter and
Appointment as text-only CodeableConcepts (temetro stores free-text
clinical values); CapabilityStatement at /fhir/metadata (unauth).
Searchset Bundles with _count/_offset pagination and self/next/prev
links; every request is org-scoped and written to the activity log.
Keys are created/revoked under Settings → Integrations (owner/admin).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/src/db/schema/fhir-keys.ts

@@ -0,0 +1,30 @@
+import { index, pgTable, text, timestamp, uuid } from "drizzle-orm/pg-core";
+
+import { organization, user } from "./auth.js";
+
+// Per-organization API keys for the read-only FHIR R4 server (`/fhir`). These
+// are machine-to-machine credentials (no Better Auth session): a caller sends
+// `Authorization: Bearer tmf_<secret>` and every query is scoped to the owning
+// clinic. Only the SHA-256 *hash* of the secret is stored — the plaintext key is
+// shown once at creation and never again. Revoking sets `revokedAt` (kept for
+// audit rather than hard-deleted).
+export const fhirApiKeys = pgTable(
+  "fhir_api_keys",
+  {
+    id: uuid("id").primaryKey().defaultRandom(),
+    organizationId: text("organization_id")
+      .notNull()
+      .references(() => organization.id, { onDelete: "cascade" }),
+    name: text("name").notNull(),
+    // Hex SHA-256 of the full `tmf_…` secret. Unique so a lookup is a single
+    // indexed probe and two keys can never collide.
+    keyHash: text("key_hash").notNull().unique(),
+    createdBy: text("created_by").references(() => user.id, {
+      onDelete: "set null",
+    }),
+    createdAt: timestamp("created_at").defaultNow().notNull(),
+    lastUsedAt: timestamp("last_used_at"),
+    revokedAt: timestamp("revoked_at"),
+  },
+  (t) => [index("fhir_api_keys_org_idx").on(t.organizationId)],
+);

backend/src/db/schema/index.ts

@@ -22,3 +22,4 @@ export * from "./meetings.js";
 export * from "./signing.js";
 export * from "./wallet-share.js";
 export * from "./wallet-updates.js";
+export * from "./fhir-keys.js";