feat: Szenario per GUI löschen, Name System-Ist reserviert (A11-T1)

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

finance/app/routers/scenarios.py

@@ -13,6 +13,7 @@ from app.db import get_session
 from app.models.tables import (Loan, ProjectionPoint, ProjectionResult,
                                Scenario, ScenarioLoan, ScenarioModifier,
                                ScenarioPlannedItem)
+from app.models.views import RESERVED_SCENARIO_NAME
 from app.services.projection_service import run_projection
 
 router = APIRouter(prefix="/api/scenarios", tags=["scenarios"],
@@ -85,6 +86,14 @@ def _get_scenario(session: Session, scenario_id: int) -> Scenario:
     return scenario
 
 
+def _check_reserved_name(name: str | None) -> None:
+    """Der Serienname der Ist-Kurve (v_projection) ist für Szenarien tabu."""
+    if name is not None and (name.strip().casefold()
+                             == RESERVED_SCENARIO_NAME.casefold()):
+        raise HTTPException(
+            422, f"Der Name »{RESERVED_SCENARIO_NAME}« ist für die Ist-Kurve reserviert")
+
+
 @router.get("", response_model=list[ScenarioOut])
 def list_scenarios(session: Session = Depends(get_session)):
     return [ScenarioOut.model_validate(s)
@@ -93,6 +102,7 @@ def list_scenarios(session: Session = Depends(get_session)):
 
 @router.post("", response_model=ScenarioOut, status_code=201)
 def create_scenario(data: ScenarioIn, session: Session = Depends(get_session)):
+    _check_reserved_name(data.name)
     if session.execute(select(Scenario).where(Scenario.name == data.name)).scalar():
         raise HTTPException(409, "Szenario existiert bereits")
     scenario = Scenario(**data.model_dump())
@@ -107,6 +117,7 @@ def patch_scenario(scenario_id: int, data: ScenarioPatch,
                    session: Session = Depends(get_session)):
     scenario = _get_scenario(session, scenario_id)
     fields = data.model_dump(exclude_unset=True)
+    _check_reserved_name(fields.get("name"))
     if "name" in fields and fields["name"] != scenario.name:
         clash = session.execute(
             select(Scenario).where(Scenario.name == fields["name"])).scalar()