refactor: modularize API routes into separate files and clean up dependencies

decnet/web/router/fleet/api_mutate_decky.py

@@ -0,0 +1,14 @@
+from fastapi import APIRouter, Depends, HTTPException
+
+from decnet.mutator import mutate_decky
+from decnet.web.dependencies import get_current_user
+
+router = APIRouter()
+
+
+@router.post("/deckies/{decky_name}/mutate", tags=["Fleet Management"])
+async def api_mutate_decky(decky_name: str, current_user: str = Depends(get_current_user)) -> dict[str, str]:
+    success = mutate_decky(decky_name)
+    if success:
+        return {"message": f"Successfully mutated {decky_name}"}
+    raise HTTPException(status_code=404, detail=f"Decky {decky_name} not found or failed to mutate")