Fix: EL-Retry bei 429 (Free-Tier-Concurrency) + index.html no-cache (immer frisches Bundle)

5 parallele EL-Calls -> 1x 502 (Concurrency-Limit). elevenlabs_tts retryt jetzt 429/5xx mit Backoff.
index.html wird nicht mehr gecacht -> nach Deploy kein altes Bundle mehr.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

voice_service/app.py

@@ -233,14 +233,26 @@ def elevenlabs_tts(text: str, voice: str) -> bytes:
         data=body,
         headers={"xi-api-key": key, "Content-Type": "application/json", "Accept": "audio/mpeg"},
     )
-    try:
-        with urllib.request.urlopen(req, timeout=60) as r:
-            return r.read()
-    except urllib.error.HTTPError as e:
-        detail = e.read()[:200].decode("utf-8", "replace")
-        raise HTTPException(502, f"ElevenLabs-Fehler {e.code}: {detail}")
-    except urllib.error.URLError as e:
-        raise HTTPException(502, f"ElevenLabs nicht erreichbar: {e}")
+    import time
+    # Free-Tier hat ein Concurrency-Limit → parallele Sätze geben 429. Retry mit Backoff fängt das ab.
+    last = ""
+    for attempt in range(4):
+        try:
+            with urllib.request.urlopen(req, timeout=60) as r:
+                return r.read()
+        except urllib.error.HTTPError as e:
+            last = f"{e.code}: {e.read()[:200].decode('utf-8', 'replace')}"
+            if e.code in (429, 500, 502, 503, 529) and attempt < 3:
+                time.sleep(0.5 * (attempt + 1))
+                continue
+            raise HTTPException(502, f"ElevenLabs-Fehler {last}")
+        except urllib.error.URLError as e:
+            last = str(e)
+            if attempt < 3:
+                time.sleep(0.5 * (attempt + 1))
+                continue
+            raise HTTPException(502, f"ElevenLabs nicht erreichbar: {last}")
+    raise HTTPException(502, f"ElevenLabs-Fehler (nach Retries): {last}")
 
 
 def elevenlabs_list() -> list[dict]: