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/repositories/pg/mod.rs

@@ -7,6 +7,7 @@ mod contact_persistence_dto;
 mod contact_pg_repository;
 mod device_code_pg_repository;
 mod favorites_pg_repository;
+pub mod file_metadata_repository;
 mod nextcloud_object_id_repository;
 mod recent_items_pg_repository;
 mod session_pg_repository;
@@ -30,6 +31,7 @@ pub use contact_persistence_dto::*;
 pub use contact_pg_repository::ContactPgRepository;
 pub use device_code_pg_repository::DeviceCodePgRepository;
 pub use favorites_pg_repository::FavoritesPgRepository;
+pub use file_metadata_repository::FileMetadataRepository;
 pub use file_blob_read_repository::FileBlobReadRepository;
 pub use file_blob_write_repository::FileBlobWriteRepository;
 pub use folder_db_repository::FolderDbRepository;