Fix seeder crash on null game data and disable SQL logging by default

Skip games with null route data (Gen 8-9 have no PokeAPI encounters)
and silence SQLAlchemy echo unless --verbose/-v is passed.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/src/app/seeds/run.py

@@ -77,6 +77,9 @@ async def seed():
                     continue
 
                 routes_data = load_json(f"{game_slug}.json")
+                if not routes_data:
+                    print(f"  {game_slug}: no route data, skipping")
+                    continue
                 route_map = await upsert_routes(session, game_id, routes_data)
                 total_routes += len(route_map)