Token-Budget Hard-Stop + Banner bei aufgebrauchtem Budget

- check_license() liefert jetzt unlimited_budget, credits_total, credits_used,
  read_only_reason. Bei nicht-unlimited UND credits_used >= credits_total wird
  status=budget_exceeded, read_only=True gesetzt.
- require_writable_license blockiert mit 403 + X-License-Status-Header je nach Reason.
- /api/auth/me liefert read_only_reason und unlimited_budget; credits_percent_used
  wird nicht mehr auf 100 gekappt (echte Prozente).
- Frontend: Banner-Text dynamisch je nach reason (budget_exceeded/expired/...).
  Refresh-Button bei read_only deaktiviert + Tooltip. Globaler 403-Handler in
  api.js: bei X-License-Status -> Banner + Toast aktualisieren.

src/services/license_service.py

@@ -11,7 +11,8 @@ async def check_license(db: aiosqlite.Connection, organization_id: int) -> dict:
     """Prueft den Lizenzstatus einer Organisation.
 
     Returns:
-        dict mit: valid, status, license_type, max_users, current_users, read_only, message
+        dict mit: valid, status, license_type, max_users, current_users, read_only,
+        read_only_reason, message, unlimited_budget, credits_total, credits_used
     """
     # Organisation pruefen
     cursor = await db.execute(
@@ -20,10 +21,14 @@ async def check_license(db: aiosqlite.Connection, organization_id: int) -> dict:
     )
     org = await cursor.fetchone()
     if not org:
-        return {"valid": False, "status": "not_found", "read_only": True, "message": "Organisation nicht gefunden"}
+        return {"valid": False, "status": "not_found", "read_only": True,
+                "read_only_reason": "not_found",
+                "message": "Organisation nicht gefunden"}
 
     if not org["is_active"]:
-        return {"valid": False, "status": "org_disabled", "read_only": True, "message": "Organisation deaktiviert"}
+        return {"valid": False, "status": "org_disabled", "read_only": True,
+                "read_only_reason": "org_disabled",
+                "message": "Organisation deaktiviert"}
 
     # Aktive Lizenz suchen
     cursor = await db.execute(
@@ -35,7 +40,15 @@ async def check_license(db: aiosqlite.Connection, organization_id: int) -> dict:
     license_row = await cursor.fetchone()
 
     if not license_row:
-        return {"valid": False, "status": "no_license", "read_only": True, "message": "Keine aktive Lizenz"}
+        return {"valid": False, "status": "no_license", "read_only": True,
+                "read_only_reason": "no_license",
+                "message": "Keine aktive Lizenz"}
+
+    # Felder zur weiteren Verwendung extrahieren
+    lic_dict = dict(license_row)
+    unlimited_budget = bool(lic_dict.get("unlimited_budget"))
+    credits_total = lic_dict.get("credits_total")
+    credits_used = lic_dict.get("credits_used") or 0
 
     # Ablauf pruefen
     now = datetime.now(TIMEZONE)
@@ -52,11 +65,21 @@ async def check_license(db: aiosqlite.Connection, organization_id: int) -> dict:
                     "status": "expired",
                     "license_type": license_row["license_type"],
                     "read_only": True,
+                    "read_only_reason": "expired",
                     "message": "Lizenz abgelaufen",
+                    "unlimited_budget": unlimited_budget,
+                    "credits_total": credits_total,
+                    "credits_used": credits_used,
                 }
         except (ValueError, TypeError):
             pass
 
+    # Budget-Check (Hard-Stop bei aufgebrauchten Credits, ausser unlimited)
+    budget_exceeded = False
+    if not unlimited_budget and credits_total and credits_total > 0:
+        if credits_used >= credits_total:
+            budget_exceeded = True
+
     # Nutzerzahl pruefen
     cursor = await db.execute(
         "SELECT COUNT(*) as cnt FROM users WHERE organization_id = ? AND is_active = 1",
@@ -64,6 +87,21 @@ async def check_license(db: aiosqlite.Connection, organization_id: int) -> dict:
     )
     current_users = (await cursor.fetchone())["cnt"]
 
+    if budget_exceeded:
+        return {
+            "valid": True,  # Lizenz ist gueltig, aber Budget aufgebraucht -> read-only
+            "status": "budget_exceeded",
+            "license_type": license_row["license_type"],
+            "max_users": license_row["max_users"],
+            "current_users": current_users,
+            "read_only": True,
+            "read_only_reason": "budget_exceeded",
+            "message": "Token-Budget aufgebraucht",
+            "unlimited_budget": False,
+            "credits_total": credits_total,
+            "credits_used": credits_used,
+        }
+
     return {
         "valid": True,
         "status": license_row["status"],
@@ -71,7 +109,11 @@ async def check_license(db: aiosqlite.Connection, organization_id: int) -> dict:
         "max_users": license_row["max_users"],
         "current_users": current_users,
         "read_only": False,
+        "read_only_reason": None,
         "message": "Lizenz aktiv",
+        "unlimited_budget": unlimited_budget,
+        "credits_total": credits_total,
+        "credits_used": credits_used,
     }