M3 plugin platform: SDK + loader, RLS-isolated tables, migrations, jobs

Backend foundation for the plugin platform (SPEC §11), Phases 1-3.

Phase 1 — SDK + loader:
- app/plugins/types.py: frozen Plugin/UiManifest/Slot/Page/JobSpec contract.
- app/plugins/sdk.py: sdk(name) facade — the only app.* import allowed for plugins
  (scoped session, plugin.{name}.* publish, blob, outbox, settings, SSRF http_get, KV, enqueue).
- app/plugins/loader.py: entry-point discovery (webmail.plugins), hook forwarding
  (API + worker), router mounting at /api/plugins/{name}, ui-manifest aggregation.
- plugin_kv core table (migration 0013) + GET /api/plugins/ui-manifest.

Phase 2 — non-removable core plugins + DB-enforced privacy:
- builtin flag (calendar/contacts will be builtin=True; uninstall refuses them).
- RLS per-user isolation on plg_* tables: least-privilege webmail_plugin role
  (migration 0014), plugin_session(user_id) sets LOCAL ROLE + app.current_user_id,
  rls.enable_rls() (ENABLE+FORCE RLS + USING/WITH CHECK policy). Mail untouched.
- Per-plugin Alembic runner (shared env, dedicated version table) + install/uninstall
  --drop-data CLI; skeleton fixture proves install -> run -> uninstall --drop-data
  leaves zero residue (§12 M3 acceptance).

Phase 3 — plugin jobs (§11.2):
- JobSpec registered as arq function plg.{plugin}.{func} + cron (5-field parser);
  singleton=True guarded by a per-(plugin,user) Redis lock; wired onto the shared
  interactive worker.

Gates: ruff, mypy --strict (94 files + tests), full suite 326 passed. RLS isolation,
migration round-trip, and singleton lock covered by tests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Rcj3TpydMTzTSmU7kunzf8

backend/workers/run.py

@@ -33,7 +33,13 @@ logger = logging.getLogger(__name__)
 _SHUTDOWN_DRAIN_S = 10.0  # §7: release leases + drain within this budget
 
 
-def _worker(functions: list[Any], queue_name: str, max_jobs: int, job_timeout: int) -> Worker:
+def _worker(
+    functions: list[Any],
+    queue_name: str,
+    max_jobs: int,
+    job_timeout: int,
+    cron_jobs: list[Any] | None = None,
+) -> Worker:
     return Worker(
         functions=functions,
         queue_name=queue_name,
@@ -41,6 +47,7 @@ def _worker(functions: list[Any], queue_name: str, max_jobs: int, job_timeout: i
         max_jobs=max_jobs,
         job_timeout=job_timeout,
         handle_signals=False,  # the runner owns signal handling (graceful shutdown)
+        cron_jobs=cron_jobs or [],
     )
 
 
@@ -49,8 +56,19 @@ def build_arq_workers(role: str) -> list[Worker]:
     s = get_settings()
     if role not in ("jobs", "all"):
         return []
+    # Plugin jobs (SPEC §11.2) join the interactive queue; cron-scheduled ones run
+    # on that worker too. With no plugins installed these are empty (inert).
+    from app.plugins.jobs import plugin_arq_functions, plugin_cron_jobs
+
+    interactive: list[Any] = [*INTERACTIVE_FUNCTIONS, *plugin_arq_functions()]
     return [
-        _worker(INTERACTIVE_FUNCTIONS, QUEUE_INTERACTIVE, s.interactive_concurrency, 120),
+        _worker(
+            interactive,
+            QUEUE_INTERACTIVE,
+            s.interactive_concurrency,
+            120,
+            cron_jobs=plugin_cron_jobs(),
+        ),
         _worker(BULK_FUNCTIONS, QUEUE_BULK, s.bulk_concurrency, 3600),
     ]
 
@@ -59,6 +77,13 @@ async def _run() -> None:
     logging.basicConfig(level=get_settings().log_level)
     role = get_settings().worker_role
 
+    # Subscribe plugin hooks so events published during sync (message.new, …) reach
+    # them in this process too (SPEC §11; the API process registers separately).
+    from app.events import get_event_bus
+    from app.plugins import loader
+
+    loader.register_hooks(get_event_bus())
+
     coordinator = SyncCoordinator() if role in ("sync", "all") else None
     if coordinator is not None:
         await coordinator.start()