chore(backend/api): rename overlay to overlays

Author: haxgun

backend/app/api/__init__.py

@@ -3,4 +3,4 @@
 from app.api.v1.endpoints import overlay
 
 api_router = APIRouter()
-api_router.include_router(overlay.router, prefix="/overlay", tags=["overlay"])
+api_router.include_router(overlay.router, prefix="/overlays", tags=["overlays"])