fix(deploy): resolve Docker startup and CSRF issues

- Rename TASKPLANER_DATA_DIR to DATA_DIR (avoid adapter-node envPrefix conflict)
- Add TASKPLANER_ORIGIN for CSRF protection in docker-compose.yml
- Add automatic database schema initialization on startup
- Add Playwright E2E tests for Docker deployment verification
- Update .env.example with correct variable names

Fixes container restart loop and 403 errors on form submission.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.env.example

@@ -16,7 +16,7 @@ PORT=3000
 # Directory for database and uploads
 # Docker: /app/data (must match volume mount)
 # Local development: ./data
-TASKPLANER_DATA_DIR=/app/data
+DATA_DIR=/app/data
 
 # ============================================
 # Production URL (REQUIRED for production)
@@ -24,8 +24,9 @@ TASKPLANER_DATA_DIR=/app/data
 
 # The full URL where users access the app
 # Used for CSRF validation and generating absolute URLs
+# Must use TASKPLANER_ prefix due to adapter-node envPrefix config
 # Example: https://tasks.example.com
-ORIGIN=http://localhost:3000
+TASKPLANER_ORIGIN=http://localhost:3000
 
 # ============================================
 # Request Limits