feat(use-case-compiler): MC-based compliance questionnaires with scoring

Implements the Use-Case Compiler that turns Master Controls into
interactive compliance audits. 5 templates (Vendor Check, SAST/DAST,
DSGVO, NIS2, CRA), deterministic + LLM question generation, scoring
engine with regulation/severity breakdown, and gap detection.

- Backend: 9 API endpoints, 22 unit tests (all pass)
- Frontend: Template selector, questionnaire, result dashboard
- Migration 027: usecase_audits + usecase_answers tables

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ai-compliance-sdk/internal/app/app.go

@@ -155,6 +155,9 @@ func buildRouter(cfg *config.Config, pool *pgxpool.Pool) *gin.Engine {
 	// Gap Analysis
 	gapHandler := handlers.NewGapHandler(pool)
 
+	// Use-Case Compiler
+	useCaseHandler := handlers.NewUseCaseHandler(pool, providerRegistry)
+
 	rbacMiddleware := rbac.NewMiddleware(rbacService, policyEngine)
 
 	// Router
@@ -179,7 +182,7 @@ func buildRouter(cfg *config.Config, pool *pgxpool.Pool) *gin.Engine {
 		uccaHandlers, escalationHandlers, obligationsHandlers, ragHandlers,
 		roadmapHandlers, workshopHandlers, portfolioHandlers,
 		academyHandlers, trainingHandlers, whistleblowerHandlers, iaceHandler,
-		gapHandler, maximizerHandlers, regulatoryNewsHandlers)
+		gapHandler, maximizerHandlers, regulatoryNewsHandlers, useCaseHandler)
 
 	return router
 }