feat(use-case-controls): relevant als Stufe statt Hard-Filter + Provenance

Der harte relevant=true-Filter versteckte ~25% des Korpus (40.926 Atome),
~70% davon echte Pflichten (500er-Validierung). relevant wird zur Stufe:

- Service: tier-Param (core=Default schuetzt Agent/CRA; all=alles inkl. review),
  ORDER BY relevant DESC; pro Control relevant/tier/source_type
  (own_library bei license_rule=3, sonst derived) + source_regulation/article;
  core_count/review_count. Pure Helper tier_label + source_type (+ Tests).
- Route: optionaler tier-Query (default core) — contract-safe (additiv).
- Frontend: Coverage-Drill-down /sdk/coverage/[useCase] — Kern-Pflichten vs.
  "zur fachlichen Pruefung", je mit Herkunfts-Badge; Uebersicht zeigt Delta.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend-compliance/compliance/api/use_case_controls_routes.py

@@ -51,6 +51,12 @@ async def controls_for_use_case(
     use_case: str,
     primary_only: bool = Query(False, description="master-grain Fallback: nur Primaerzweck"),
     sub_topic: Optional[str] = Query(None, description="atom-grain: nur dieses Sub-Thema"),
+    tier: str = Query(
+        "core",
+        pattern="^(core|all)$",
+        description="atom-grain: 'core'=nur validierte Kern-Pflichten (Default), "
+        "'all'=alle inkl. 'zur Prüfung'-Stufe",
+    ),
     limit: int = Query(50, ge=1, le=200),
     offset: int = Query(0, ge=0),
     svc: UseCaseControlsService = Depends(get_use_case_controls_service),
@@ -58,4 +64,4 @@ async def controls_for_use_case(
     """Controls for a topic. Atom-grain (Haiku: relevant + sub_topic) wenn vorhanden,
     sonst master-grain Seed."""
     with translate_domain_errors():
-        return svc.controls_for_use_case(use_case, primary_only, limit, offset, sub_topic)
+        return svc.controls_for_use_case(use_case, primary_only, limit, offset, sub_topic, tier)