feat: AI photo enhancement (Real-ESRGAN container) + restore original

- new photo-ai service: FastAPI + Real-ESRGAN x2plus on CPU, internal only
- async job queue in server (POST enhance-ai / GET status), 5min timeout, sequential processing
- keep original photo backup (entries.photo_original_path, uploads/.originals), restore-original endpoint
- UI: AI button and restore-original button in enhance modal
- db: photo_original_path column (init.sql, migration.sql, runtime ensure)

db/init.sql

@@ -42,6 +42,7 @@ CREATE TABLE IF NOT EXISTS entries (
   ai_checked_at TIMESTAMPTZ,
   ai_error TEXT,
   photo_path VARCHAR(255),
+  photo_original_path VARCHAR(255),
   deleted_at TIMESTAMPTZ,
   created_at TIMESTAMPTZ DEFAULT now()
 );