Security fixes: P0-P2 complete (22 fixes)

P0 (7): Auth-bypass removed, migrations fixed, plugin-upload disabled, RLS FORCE+WITH CHECK, plugin double-registration fixed, persistent volume, domain removed
P1 (11): User/tenant model, Redis centralized, worker separated, transactional outbox, XSS fixed, DMS chunked streaming, permissions unified, password reset, metrics secured, config/docs fixed, cross-tenant FK
P2 (4): Contact model normalized, cross-imports reduced 94%, commands+state machines for contacts/dms/mail/calendar, SPA path-traversal

8 new migrations, 99 unit tests, 13 commands, 8 contracts, 72 files changed

app/plugins/builtins/unified_search/query_understanding.py

@@ -38,7 +38,7 @@ async def _get_api_credentials(
     """
     if db and tenant_id:
         try:
-            from app.plugins.builtins.ai_assistant.services import get_default_provider
+            from app.plugins.builtins.ai_assistant.contracts import get_default_provider
             provider = await get_default_provider(db, tenant_id)
             if provider and provider.api_key:
                 return provider.api_key, provider.base_url, provider.provider_type