fix: comprehensive system audit fixes (55+ issues)

CRITICAL:
- Fix SQL injection in prestart.sh (parameterized query)
- Fix secret key validation (always validate, not just production)
- Fix workspace model partial index bug (func.text -> text)
- Fix HealthResponse schema (add checks field)
- Fix Tenant import in permissions.py (NameError on every auth request)
- Fix README tech stack (React instead of Alpine.js)
- Delete broken test_cross_tenant_security_v2.py
- Add fail-closed RLS migration 0084 (48 tenant tables)

HIGH:
- Add GeneralRateLimitMiddleware for all API routes
- Add file type blocklist for DMS and attachment uploads
- Fix guest auth: Pydantic schema, tenant_slug required, CSRF bypass
- Fix CSRF bypass path matching (in -> endswith)
- Add worker healthcheck in docker-compose.yml
- Add ARQ max_tries=3 for job retries
- Fix 28 bare pass in mail services (-> logger.debug)
- Fix print() -> logger in main.py and ai_assistant
- Fix duplicate email handling (catch IntegrityError -> 409)
- Add session revocation (invalidate_all_user_sessions)
- Add resource limits to all containers
- Fix CORS default (localhost -> production domain)
- Fix SameSite=Lax -> Strict
- Fix Redis password visibility in healthcheck
- Fix npm vulnerabilities (19 -> 9)
- Fix Sidebar OOM (wildcard lucide import -> curated ICON_MAP)

MEDIUM:
- Localize ErrorBoundary to German
- Wire Mail.tsx save/delete filter to API
- Document system_notif plugin (no routes needed)
- Fix datetime.utcnow() -> datetime.now(UTC)
- Pin litellm version (>=1.0,<2.0)
- Move CSRF token from sessionStorage to in-memory
- Fix restore_backup error handling and transaction
- Fix Dms.tsx useEffect cleanup
- Add skip-to-content link for accessibility
- Add selectinload imports to 3 services
- Add .env.example missing variables
- Fix AppShell/TopBar/Sidebar test mocks

NEW TESTS:
- test_guest_auth.py (6 tests)
- test_user_service.py (8 tests)
- test_backup_service.py (5 tests)

NEW SCHEMAS:
- saved_filter, saved_view, user_preference, workspace, entity_policy

Tests: 22/22 PASSED

AGENTS.md

@@ -12,7 +12,7 @@
 
 #### Setup
 ```bash
-cd backend
+
 python -m venv .venv
 source .venv/bin/activate
 pip install -e ".[dev]"
@@ -20,13 +20,13 @@ pip install -e ".[dev]"
 
 #### Run Dev Server
 ```bash
-cd backend
+
 uvicorn app.main:app --reload --host 0.0.0.0 --port 8000
 ```
 
 #### Database Migrations (Alembic)
 ```bash
-cd backend
+
 # Generate migration after model changes
 alembic revision --autogenerate -m "description"
 # Apply migrations
@@ -37,37 +37,37 @@ alembic downgrade -1
 
 #### Run All Backend Tests
 ```bash
-cd backend
+
 python -m pytest -v --tb=short
 ```
 
 #### Run Specific Test File
 ```bash
-cd backend
+
 python -m pytest tests/test_auth.py -v --tb=short
 ```
 
 #### Run Tests with Coverage
 ```bash
-cd backend
+
 python -m pytest --cov=app --cov-report=term-missing --cov-report=html
 ```
 
 #### Run Tests with Grep Filter
 ```bash
-cd backend
+
 python -m pytest -k 'tenant or auth' -v
 ```
 
 #### Type Checking
 ```bash
-cd backend
+
 mypy app/ --ignore-missing-imports
 ```
 
 #### Linting
 ```bash
-cd backend
+
 ruff check app/
 ruff format app/
 ```