fix(use-cases): Verifikations-Methode aus Primaer-Use-Case ableiten (Fallback)

Member-canonical_controls tragen meist kein evidence_type/verification_method
(wie schon source_citation). primary_verification_method() leitet die Methode
deterministisch aus dem Primaer-Use-Case ab (impressum->document,
code_security->source_code, ...). Populiert mc_verification beim naechsten Seed.

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

backend-compliance/scripts/classify_mc_use_cases.py

@@ -107,7 +107,9 @@ async def run_seed(conn, limit: int = 0) -> dict:
                 mc_uuid, mc_id, uc, is_prim)
             n_uc += 1
         n_mc += 1
-        m = verif.get(mc_uuid)
+        # Verifikations-Methode: Member-evidence oder (Fallback) aus dem
+        # Primaer-Use-Case ableiten (Member tragen oft kein evidence_type).
+        m = verif.get(mc_uuid) or reg.primary_verification_method(uc_primary)
         if m:
             await conn.execute(
                 """INSERT INTO compliance.mc_verification