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>

pb_hooks/entra_oidc.pb.js

@@ -0,0 +1,34 @@
+/// <reference path="../pb_data/types.d.ts" />
+//
+// Issue #18 — Reconcile the Entra (Azure) OIDC provider from the environment.
+//
+// The team_members→auth migration (pb_migrations/1781000000) is structure-only
+// and runs exactly once. Provider CONFIGURATION lives here instead, so that:
+//
+//   * an environment whose migration applied while the ENTRA_* secrets were
+//     absent gets its provider enabled on the next startup (no re-apply),
+//   * rotating ENTRA_CLIENT_SECRET / changing the tenant only requires new env
+//     values and a container restart,
+//   * a fresh database gets its provider on the first cron tick right after
+//     the migrations created the collection (onBootstrap fires BEFORE the
+//     migrations run — there is no post-migration lifecycle hook in the JSVM,
+//     hence the cron fallback).
+//
+// The reconciler compares before saving, so both hooks are cheap no-ops when
+// everything is already in sync.
+
+onBootstrap((e) => {
+  e.next();
+  const { reconcileEntraOidc } = require(`${__hooks}/utils.js`);
+  // reconcileEntraOidc logs a warn-once itself when the ENTRA_* env is absent.
+  console.log("entra_oidc reconcile (bootstrap): " + reconcileEntraOidc(e.app));
+});
+
+cronAdd("entraOidcReconcile", "* * * * *", () => {
+  const { reconcileEntraOidc } = require(`${__hooks}/utils.js`);
+  const result = reconcileEntraOidc($app);
+  // Only log state changes — this tick runs every minute.
+  if (result === "updated") {
+    console.log("entra_oidc reconcile (cron): OIDC provider (re)configured from ENTRA_* env");
+  }
+});