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>

.dockerignore

@@ -1,46 +1,44 @@
+# Python-generated files
+__pycache__/
+*.py[oc]
+build/
+dist/
+wheels/
+*.egg-info
+
+# Virtual environments
+.venv
+venv/
+
+# Database files (will be mounted as volume)
+*.db
+
+# OS generated files
+.DS_Store
+.DS_Store?
+._*
+.Spotlight-V100
+.Trashes
+ehthumbs.db
+Thumbs.db
+
 # Git
 .git
 .gitignore
 
-# Python
-__pycache__/
-*.py[cod]
-*$py.class
-*.so
-.Python
-env/
-build/
-develop-eggs/
-dist/
-downloads/
-eggs/
-.eggs/
-lib/
-lib64/
-parts/
-sdist/
-var/
-*.egg-info/
-.installed.cfg
-*.egg
-
-# Virtual Environment
-venv/
-ENV/
-
-# IDE
-.idea/
+# IDE files
 .vscode/
+.idea/
 *.swp
 *.swo
 
-# Database
-*.db
+# Logs
+logs/
+*.log
 
-# Uploads
-static/uploads/*
-!static/uploads/.gitkeep
+# Development files
+.env
+.env.local
 
-# Docker
-Dockerfile
-.dockerignore 
+# Cache directories
+.cache/