feat: Tarife einstellbar + 15 weitere Filler + Mitteilung bei Leer-Antwort

- Strompreis (EUR/kWh), Notruf-Kosten (EUR/Alarm), Cartesia ($/Zeichen) jetzt im
  Admin live einstellbar (RUNTIME_SETTABLE).
- OPENING-Beruhigungssaetze 12 -> 27 (random.choice; formale "Sie"-Uebersetzung
  ersetzt beim Neustart den alten "dich"-Cache).
- Leer-/kein-Treffer-Antwort: statt Stille eine freundliche lokalisierte
  Mitteilung ("Dazu konnte ich keine Informationen finden."), gesprochen.

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

app/pipeline/fillers.py

@@ -35,6 +35,21 @@ OPENING_PHRASES = [
     "Give me a second, I'll find that out for you.",
     "I'm checking that for you now, one moment please.",
     "Let me look that up so I can tell you exactly.",
+    "Let me check the current details for you — it won't take long.",
+    "I'll find the up-to-date answer for you, one moment.",
+    "Allow me a brief moment to look into that.",
+    "Let me gather the latest information for you.",
+    "I'm on it — just give me a short moment.",
+    "Let me make sure I have the current facts for you.",
+    "One moment please, I'm fetching the latest for you.",
+    "Let me quickly check what's current on that.",
+    "I'll look into that for you right away, just a moment.",
+    "Bear with me a second while I find that out.",
+    "Let me get you the most recent information on that.",
+    "Just a brief moment — I'm checking the latest for you.",
+    "I'll dig that up for you now, one moment please.",
+    "Let me find the current answer so I can tell you properly.",
+    "Let me take a quick look and find that out for you.",
 ]
 
 PATIENCE_PHRASES = [