feat: Credits-System — Token-Usage-Router, Budget-Verwaltung, Frontend-Übersicht

- Neuer Router /api/token-usage mit Overview, Org-Detail, Monatsstatistik
- Budget-Felder (credits_total, cost_per_credit, token_budget_usd) bei Lizenz-Erstellung
- Token-Nutzung Sub-Tab in Org-Detail mit Verbrauchsbalken und Monatstabelle
- Dashboard Stat-Card für API-Kosten gesamt
- CSS Dark-Theme Styling für Token-Komponenten

src/models.py

@@ -40,6 +40,10 @@ class LicenseCreate(BaseModel):
     license_type: str = Field(pattern="^(trial|annual|permanent)$")
     max_users: int = Field(default=5, ge=1, le=1000)
     duration_days: Optional[int] = Field(default=None, ge=1, le=3650)
+    token_budget_usd: Optional[float] = None
+    credits_total: Optional[int] = None
+    cost_per_credit: Optional[float] = None
+    budget_warning_percent: Optional[int] = Field(default=80, ge=1, le=100)
 
 
 class LicenseResponse(BaseModel):
@@ -51,6 +55,11 @@ class LicenseResponse(BaseModel):
     valid_until: Optional[str]
     status: str
     notes: Optional[str]
+    token_budget_usd: Optional[float] = None
+    credits_total: Optional[int] = None
+    credits_used: Optional[float] = None
+    cost_per_credit: Optional[float] = None
+    budget_warning_percent: Optional[int] = None
     created_at: str