feat: update Docker setup for refactored app structure

- Update Dockerfile to copy new app/ directory structure
- Fix docker-compose.yml volume paths for app/static/uploads
- Add environment variable support for new config system
- Update migration service to use migrate_session_changes.py
- Add .dockerignore for optimized builds
- Remove obsolete version field from docker-compose.yml
- Create comprehensive README_DOCKER.md documentation

The Docker setup now fully supports the refactored Flask application
with modular structure, authentication, and like system.

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

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

Dockerfile

@@ -15,11 +15,13 @@ RUN pip install uv
 # Copy project files
 COPY pyproject.toml .
 COPY main.py .
-COPY templates/ templates/
+COPY app/ app/
+COPY migrate_session_changes.py .
+COPY README_MIGRATION.md .
 COPY README.md .
 
-# Create uploads directory
-RUN mkdir -p static/uploads
+# Create uploads directory in the correct location
+RUN mkdir -p app/static/uploads
 
 # Create and activate virtual environment, then install dependencies
 RUN uv venv && \