fix: heal migration-ledger mismatch and make Azure SSO deploy-proof (#18)

PocketBase on Labs crash-looped since the SSO deploy (PR #17): mounting
--migrationsDir for the first time replayed the entire migration history
against a database that was provisioned out-of-band (empty _migrations
ledger) and died on 1778948471_created_content.js. On top of that the
team_members->auth migration had its own crash paths and trapped OAuth2
config inside a one-shot, env-dependent migration.

- pb_migrations/1000000000_baseline_ledger_sync.js: detects an
  out-of-band provisioned DB (schema exists, ledger empty) and marks the
  79 historical migrations as applied; no-op on fresh or already-synced DBs
- pb_migrations/1781000000_team_members_to_auth.js: idempotency guard,
  relation->text conversion WITH data preservation (PocketBase diffs
  fields by id, so the column is backed up and restored via SQL), unique
  index rebuild, no silent catches, env only as fast-path
- pb_hooks/entra_oidc.pb.js + pb_hooks/utils.js: reconcile the Entra OIDC
  provider from ENTRA_* env on every bootstrap + cron tick
  (compare-before-save, warn-once); heals environments that migrated
  without secrets and supports secret rotation without re-apply
- pb_hooks/team_members.pb.js: require() pattern — JSVM runs callbacks as
  isolated programs, top-level helpers are not in scope (adopts Leroy's
  fix from the fix-sso branch)
- infra/*/site/deploy-playbook.yml: health-gate after compose up — the
  deploy fails loudly with container logs when PocketBase does not become
  healthy (runs #83-#88 were green while PB crash-looped)
- docker-compose.yml: .env.local is optional again
- docs/auth-spec.md + AI_AGENT.md: ledger/reconciler documentation, ADRs
  006-008, never-rename-applied-migrations warning

Verified locally against PocketBase v0.30.4 with a 7-scenario DoD matrix
(fresh DB +/- env, out-of-band DB with data incl. data preservation,
populated-ledger upgrade, late-secrets healing, re-run guard, hook
provisioning): 15/15 pass. npm test 112/112.

Closes #18

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

infra/development/site/deploy-playbook.yml

@@ -72,3 +72,31 @@
         state: present
         files: compose.yml
         recreate: always
+
+    # A failed migration aborts `pocketbase serve` and the container crash-loops
+    # while `docker compose up` still reports success (issue #18). Gate the
+    # deploy on PocketBase actually serving its health endpoint.
+    - name: Wait for PocketBase to become healthy
+      ansible.builtin.command: docker exec pocketbase-learning wget -q -O - http://127.0.0.1:8090/api/health
+      register: pb_health
+      until: pb_health.rc == 0
+      retries: 18
+      delay: 5
+      changed_when: false
+      ignore_errors: yes
+
+    - name: Collect PocketBase logs for diagnosis
+      ansible.builtin.command: docker logs --tail 80 pocketbase-learning
+      register: pb_logs
+      when: pb_health is failed
+      changed_when: false
+      failed_when: false
+
+    - name: Abort deploy — PocketBase is not healthy
+      ansible.builtin.fail:
+        msg: |
+          PocketBase did not become healthy after the deploy (health endpoint unreachable).
+          Recent container logs:
+          {{ pb_logs.stdout | default('') }}
+          {{ pb_logs.stderr | default('') }}
+      when: pb_health is failed