feat(use-cases): deterministisches source_regulation-Mapping + Primaerzweck [migration-approved]

Use-Case-Zuordnung jetzt DETERMINISTISCH aus der Quell-Regulierung (statt
LLM/scope-category): control_parent_links.source_regulation (79% der 13.588
MCs) -> Keyword-Mapper -> ~30 Domaenen-Use-Cases. 117/117 Regulierungen
gemappt (dse 44 Leitlinien, code_security 10, network_security 9, ...).

- use_case_registry.py: 37 Use Cases (Doku + Security + Produkt/Sektor:
  cra/ai_act/mica/mdr/maschinen/batterie/ehds/dsa/dma/psd2/aml/lksg/...) +
  use_case_for_regulation() Keyword-Mapper (117 Regulierungen abgedeckt).
- migration 150: is_primary auf mc_use_case_mappings + neue mc_regulations
  (MC->source_regulation, n:m, is_primary) als feine Filter-Dimension.
- classify_mc_use_cases.py: source_regulation-getriebener Seed; Primaerzweck =
  dominante Regulierung, Mehrfachzwecke = weitere. PYTHONPATH-Bootstrap.
- 18 Registry-Tests gruen (Mapper-Abdeckung + Konsistenz-Invariante).

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

backend-compliance/tests/test_use_case_registry.py

@@ -110,3 +110,38 @@ def test_seed_empty_and_none_safe():
                                vmethods=[None], etypes=[None])
     assert ucs == [] and m is None
     assert reg.seed_classify() == ([], None)
+
+
+# ── Deterministischer Regulierung→Use-Case-Mapper ───────────────────
+
+
+def test_regulation_mapper_known():
+    cases = {
+        "OWASP Top 10 (2021)": "code_security",
+        "NIST SP 800-207 (Zero Trust)": "network_security",
+        "Cyber Resilience Act (CRA)": "cra",
+        "DSGVO (EU) 2016/679": "dse",
+        "EDPB Facial Recognition": "dse",      # Leitlinie → Datenschutz
+        "TKG": "impressum",
+        "TDDDG": "cookie_banner",
+        "Markets in Crypto-Assets (MiCA)": "mica",
+        "BGB": "agb",
+    }
+    for reg_str, expected in cases.items():
+        assert reg.use_case_for_regulation(reg_str) == expected, reg_str
+
+
+def test_regulation_mapper_abgb_before_bgb():
+    # 'ABGB' enthaelt 'bgb' — die abgb-Regel MUSS zuerst greifen.
+    assert reg.use_case_for_regulation("AT ABGB") == "handelsrecht"
+
+
+def test_regulation_mapper_unknown_returns_none():
+    assert reg.use_case_for_regulation("Voellig Unbekanntes Gesetz") is None
+    assert reg.use_case_for_regulation(None) is None
+
+
+def test_all_regulation_rules_point_to_valid_use_cases():
+    for _needle, uc in reg._REGULATION_RULES:
+        assert uc in reg.REGISTRY, uc
+        assert reg.REGISTRY[uc].enabled