feat: Implement Step 12 - File System with MinIO S3 Storage

Completed File Management Service with S3-compatible object storage:

Infrastructure:
- Added MinIO for S3-compatible object storage (port 9000/9001)
- Integrated with MongoDB for metadata management
- Configured Docker volumes for persistent storage

File Service Features:
- Multi-file upload support with deduplication
- Automatic thumbnail generation for images (multiple sizes)
- File metadata management with search and filtering
- Presigned URLs for secure direct uploads/downloads
- Public/private file access control
- Large file upload support with chunking
- File type detection and categorization

API Endpoints:
- File upload (single and multiple)
- File retrieval with metadata
- Thumbnail generation and caching
- Storage statistics and analytics
- Bucket management
- Batch operations support

Technical Improvements:
- Fixed Pydantic v2.5 compatibility (regex -> pattern)
- Optimized thumbnail caching strategy
- Implemented file hash-based deduplication

Testing:
- All services health checks passing
- MinIO and file service fully operational
- Ready for production use

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

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

services/files/backend/requirements.txt

@@ -0,0 +1,11 @@
+fastapi==0.109.0
+uvicorn[standard]==0.27.0
+pydantic==2.5.3
+python-dotenv==1.0.0
+motor==3.5.1
+pymongo==4.6.1
+minio==7.2.3
+pillow==10.2.0
+python-magic==0.4.27
+aiofiles==23.2.1
+python-multipart==0.0.6