refactor: remove netplan apply endpoint and related code

backend/src/main.py

@@ -60,35 +60,3 @@ def nft_ruleset():
 # ---------------------
 
 app.include_router(network_api.router, prefix="/network", tags=["network"])
-
-
-# ---------------------
-#   Netplan Apply
-# ---------------------
-
-NETPLAN_FILE = "/etc/netplan/99-app.yaml"
-
-@app.post("/netplan/apply")
-def apply_netplan(config: netplan.NetworkConfig):
-    try:
-        data = {"network": config.dict(exclude_none=True)}
-
-        with open(NETPLAN_FILE, "w") as f:
-            yaml.dump(data, f, sort_keys=False)
-
-        result = subprocess.run(
-            ["netplan", "try", "--timeout", "10"],
-            capture_output=True,
-            text=True,
-        )
-
-        if result.returncode != 0:
-            raise HTTPException(
-                status_code=500,
-                detail=f"Netplan failed: {result.stderr}"
-            )
-
-        return {"status": "ok", "output": result.stdout}
-
-    except Exception as e:
-        raise HTTPException(status_code=500, detail=str(e))