Add test utilities and Jellyfin audio conventions doc

- test_ean_scan.py: interactive EAN barcode scanning test via scanner server
- test_backcover_scan.py: comprehensive backcover metadata extraction test
- docs/Grundsaetzliche_Audio_Koventionen_und_Methoden_Jellyfin.md: notes on
  audio conventions and naming methods for Jellyfin

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

test_ean_scan.py

@@ -0,0 +1,107 @@
+#!/usr/bin/env python3
+"""Interaktiver EAN-Scan-Test: Foto hochladen → Vision-LLM → EAN ausgeben.
+
+Starten: python3 test_ean_scan.py
+Beenden: Strg+C
+"""
+
+import base64
+import re
+import sys
+from pathlib import Path
+
+import httpx
+
+from musiksammlung.scanner_server import ScannerServer, print_qr
+from musiksammlung.vision_llm import EAN_PROMPT
+
+UPLOAD_DIR = Path("/tmp/ean_scan_test")
+PORT = 8765
+MODEL = "qwen3-vl:235b-cloud"
+BASE_URL = "http://localhost:11434"
+TIMEOUT_PHOTO = 300.0   # Sekunden warten auf Foto-Upload
+TIMEOUT_LLM   = 60.0    # Sekunden warten auf LLM-Antwort
+
+
+def query_llm(image_path: Path) -> str:
+    """Schickt das Bild ans Vision-LLM und gibt die Rohausgabe zurück."""
+    b64 = base64.b64encode(image_path.read_bytes()).decode()
+    response = httpx.post(
+        f"{BASE_URL}/api/chat",
+        json={
+            "model": MODEL,
+            "messages": [{"role": "user", "content": EAN_PROMPT, "images": [b64]}],
+            "stream": False,
+        },
+        timeout=TIMEOUT_LLM,
+    )
+    response.raise_for_status()
+    return response.json()["message"]["content"]
+
+
+def extract_ean(raw: str) -> str | None:
+    """Bereinigt Rohausgabe und extrahiert Ziffernfolge."""
+    cleaned = re.sub(r"<think>.*?</think>", "", raw, flags=re.DOTALL).strip()
+    digits = re.sub(r"\D", "", cleaned)
+    return digits if digits else None
+
+
+def run() -> None:
+    UPLOAD_DIR.mkdir(parents=True, exist_ok=True)
+    server = ScannerServer(port=PORT, upload_dir=UPLOAD_DIR)
+    server.start()
+
+    print(f"\nModel:  {MODEL}")
+    print(f"Prompt: {EAN_PROMPT!r}\n")
+    print_qr(server.url())
+    print(f"Upload-URL: {server.url()}\n")
+
+    runde = 0
+    try:
+        while True:
+            runde += 1
+            print(f"\n{'─'*50}")
+            print(f"Runde {runde}: Bitte Foto hochladen — URL: {server.url()}")
+            print(f"(Timeout {TIMEOUT_PHOTO:.0f}s — Formular auf dem Handy lädt sich nach 3s selbst zurück)")
+            photo = server.get_photo(timeout=TIMEOUT_PHOTO)
+
+            if photo is None:
+                print("Timeout — kein Foto empfangen. Nochmal? (j/n) ", end="", flush=True)
+                if input().strip().lower() not in ("j", "ja", "y", "yes"):
+                    break
+                continue
+
+            print(f"Foto empfangen: {photo}  ({photo.stat().st_size} Bytes)")
+            print(f"LLM-Anfrage läuft ({MODEL}) ...")
+
+            try:
+                raw = query_llm(photo)
+            except Exception as exc:
+                print(f"LLM-Fehler: {exc}")
+                continue
+
+            print(f"\nRohantwort:\n  {raw!r}")
+
+            cleaned = re.sub(r"<think>.*?</think>", "", raw, flags=re.DOTALL).strip()
+            if cleaned != raw.strip():
+                print(f"Nach Think-Tag-Entfernung:\n  {cleaned!r}")
+
+            ean = extract_ean(raw)
+            if ean:
+                print(f"\n✓ EAN erkannt: {ean}  ({len(ean)} Stellen)")
+            else:
+                print("\n✗ Kein Barcode erkannt")
+
+            print("\nNochmal? (j/n) ", end="", flush=True)
+            if input().strip().lower() not in ("j", "ja", "y", "yes"):
+                break
+
+    except KeyboardInterrupt:
+        print("\nAbgebrochen.")
+    finally:
+        server.stop()
+        print("Server gestoppt.")
+
+
+if __name__ == "__main__":
+    run()