feat(photos): add EXIF metadata extraction and storage

Extract EXIF orientation, GPS coordinates, camera info, and timestamps
from uploaded images using kamadak-exif. Store metadata in a new
file_metadata PG table. Apply EXIF orientation to thumbnail generation
so images display correctly. Add /api/files/{id}/metadata endpoint.

src/infrastructure/services/mod.rs

@@ -1,6 +1,7 @@
 pub mod chunked_upload_service;
 pub mod compression_service;
 pub mod dedup_service;
+pub mod exif_service;
 pub mod file_content_cache;
 pub mod file_system_i18n_service;
 pub mod image_transcode_service;