Change video storage directory from /storage to /mnt/nfs_share

- Update StorageConfig default base_path in core/config.py
- Update base_path and camera storage_paths in config.json and config.compose.json
- Update Docker Compose volume mounts to use /mnt/nfs_share
- Update start_system.sh to create /mnt/nfs_share directory
- Update convert_avi_to_mp4.sh to use new NFS path
- Update all documentation files to reflect new storage paths
- Videos now stored on NFS server at 192.168.1.249:/mnt/nfs_share/

camera-management-api/docs/API_DOCUMENTATION.md

@@ -196,7 +196,7 @@ GET /cameras/{camera_name}/config
 {
   "name": "camera1",
   "machine_topic": "blower_separator",
-  "storage_path": "/storage/camera1",
+  "storage_path": "/mnt/nfs_share/camera1",
   "exposure_ms": 0.3,
   "gain": 4.0,
   "target_fps": 0,
@@ -306,7 +306,7 @@ GET /storage/stats
 **Response**: `StorageStatsResponse`
 ```json
 {
-  "base_path": "/storage",
+  "base_path": "/mnt/nfs_share",
   "total_files": 150,
   "total_size_bytes": 5368709120,
   "cameras": {