fix(audio): support HEAD method on audio proxy route

app/main.py

@@ -158,7 +158,7 @@ async def api_lookup(q: str = Query(..., min_length=1), user: dict = Depends(req
     result = await lookup_term(q)
     return result
 
-@app.get("/api/audio")
+@app.api_route("/api/audio", methods=["GET", "HEAD"])
 async def api_audio_proxy(file: str = Query(..., min_length=1)):
     """Proxies Wikimedia audio file with required User-Agent."""
     cleaned_file = urllib.parse.unquote(file).strip()