Remove obsolete files and clean up repository structure

Removed unused files:
- oidc-middleware.js (unused OIDC authentication code)
- package.json (dependencies for unused middleware)
- healthcheck.js (Cloudron uses manifest healthCheckPath instead)

Updated Dockerfile to remove healthcheck.js references.
Updated DEPLOYMENT.md to reflect current repository structure.

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

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

DEPLOYMENT.md

@@ -60,8 +60,8 @@ docmost-cloudron/
 ├── start.sh                   # Startup script
 ├── nginx.conf                 # Reverse proxy
 ├── supervisord.conf           # Process management
-├── oidc-middleware.js         # Authentication (future)
-├── package.json              # Dependencies
+├── env.sample                 # Configuration template
+├── CONFIGURATION.md           # User documentation
 ├── README.md                  # Documentation
 └── DEPLOYMENT.md             # This file
 ```