feat(rechner): Saetze per Regler einstellbar mit Empfehlung aus 30-Tage-API-Kosten

Neuer Router pricing.py (GET /api/pricing/cost-basis), liest die geteilte
Live-DB read-only und liefert Median-Kosten je Lagentyp plus Credit-Empfehlung.
main.py um den Router erweitert. Frontend rechner.js mit Reglern statt fester
Saetze und Empfehlungsanzeige je Aktion.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/main.py

@@ -11,7 +11,7 @@ from fastapi.staticfiles import StaticFiles
 from fastapi.responses import FileResponse
 
 from config import STATIC_DIR, PORT
-from routers import auth, organizations, licenses, users, dashboard, sources, token_usage, audit, translation, x_scraper
+from routers import auth, organizations, licenses, users, dashboard, sources, token_usage, audit, translation, x_scraper, pricing
 
 logging.basicConfig(
     level=logging.INFO,
@@ -44,6 +44,7 @@ app.include_router(token_usage.router)
 app.include_router(audit.router)
 app.include_router(translation.router)
 app.include_router(x_scraper.router)
+app.include_router(pricing.router)
 
 # --- Statische Dateien ---
 app.mount("/static", StaticFiles(directory=STATIC_DIR), name="static")