feat(llm): Live-Parameter top_p + Live/Restart-Kennzeichnung — Plan-Schritt 4

- local_llm_top_p (Default 0.9) durch Config -> runtime_config (RUNTIME_SETTABLE,
  live ohne Neustart) -> local-openai-compatible Payload (top_p).
- Admin-Einstellungen: top_p als Slider (0–1); Hints "wirkt sofort (kein Neustart)"
  für temperature/top_p.
- Doku: top_p + Klarstellung Live-Parameter (temp/top_p/max_tokens) vs.
  Startup-Wert Kontextfenster (OLLAMA_CONTEXT_LENGTH / llama.cpp -c).

Verifiziert: top_p im Payload, Live-Config-Round-Trip (PUT/DELETE). 165 grün.

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

app/runtime_config.py

@@ -26,7 +26,8 @@ RUNTIME_SETTABLE: dict[str, tuple[str, str, str]] = {
     "openrouter_tts_voice":          ("TTS-Stimme (OpenRouter)",       "str",   "z.B. Zephyr, Puck, Kore"),
     "piper_voice":                   ("TTS-Stimme (piper)",            "str",   "z.B. de_DE-thorsten-high"),
     "local_llm_system_prompt":       ("Systemprompt (lokal)",          "str",   "Freier Text"),
-    "local_llm_temperature":         ("Temperatur (lokal)",            "float", "0.0–2.0"),
+    "local_llm_temperature":         ("Temperatur (lokal)",            "float", "0.0–2.0 — wirkt sofort (kein Neustart)"),
+    "local_llm_top_p":               ("Top-p (lokal)",                 "float", "0.0–1.0 — wirkt sofort (kein Neustart)"),
     "local_llm_max_tokens":          ("Max. Tokens (lokal)",           "int",   "0 = kein Limit"),
     "tts_normalize_level":           ("TTS-Normalisierung",            "str",   "auto | full | light | off"),
     "audio_stream_default":          ("Audio-Streaming Standard",      "bool",  "true | false"),