Fixes CSRF race condition where every GET rotated the CSRF token,
causing POST failures when users had multiple tabs or slow connections.
Changes:
- Remove fastapi-csrf-protect dependency
- Add session-bound CSRF tokens stored in config.sessions table
- Add pre-auth CSRF for unauthenticated routes (/login, /setup/operator)
- Add csrf.py module for pre-auth token generation/validation
- Update routes to use new CSRF token handling
- Add migration 013 to add csrf_token column to sessions
The session-bound approach ensures CSRF tokens remain stable for the
duration of a session, eliminating the race condition.
Note: Route tests (test_wizard.py, test_adapters.py, etc.) need
refactoring to mock get_settings() instead of CsrfProtect dependency.
Core auth/CSRF handler tests pass (74 tests).
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
