feat: Präfix System- für Tool-Serien reserviert, Kreditraten-Serie heißt System-Kreditraten (A12-T1)

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

finance/app/routers/categories.py

@@ -6,6 +6,7 @@ from sqlalchemy.orm import Session
 from app.auth import require_auth
 from app.db import get_session
 from app.models.tables import Category, CategoryRule
+from app.reserved import check_reserved_name
 
 router = APIRouter(prefix="/api", tags=["categories"],
                    dependencies=[Depends(require_auth)])
@@ -39,6 +40,7 @@ def list_categories(session: Session = Depends(get_session)):
 
 @router.post("/categories", response_model=CategoryOut, status_code=201)
 def create_category(data: CategoryIn, session: Session = Depends(get_session)):
+    check_reserved_name(data.name)
     if session.execute(select(Category).where(Category.name == data.name)).scalar():
         raise HTTPException(409, "Kategorie existiert bereits")
     cat = Category(**data.model_dump())
@@ -51,6 +53,7 @@ def create_category(data: CategoryIn, session: Session = Depends(get_session)):
 @router.patch("/categories/{category_id}", response_model=CategoryOut)
 def patch_category(category_id: int, data: CategoryIn,
                    session: Session = Depends(get_session)):
+    check_reserved_name(data.name)
     cat = session.get(Category, category_id)
     if cat is None:
         raise HTTPException(404, "Kategorie nicht gefunden")