fix: resolve database and session initialization issues

- Switch from SQLAlchemy sessions to filesystem sessions to avoid race
  conditions with multiple gunicorn workers trying to create the sessions
  table simultaneously
- Update Alembic env.py to use a minimal Flask app without Flask-Session
  to prevent session table creation during migrations
- Add data directory creation to entrypoint.sh for clean container starts
- Configure test environment to use filesystem sessions with temp directory

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

entrypoint.sh

@@ -1,6 +1,9 @@
 #!/bin/bash
 set -e  # Exit on any error
 
+# Ensure data directory exists
+mkdir -p /app/data
+
 echo "Running database migrations..."
 if uv run alembic upgrade head; then
     echo "Database migrations completed successfully"