feat: evidence_type Feld (code/process/hybrid) fuer Controls

Neues Feld auf canonical_controls klassifiziert, ob ein Control
technisch im Source Code (code), organisatorisch via Dokumente (process)
oder beides (hybrid) nachgewiesen wird. Inklusive Backfill-Endpoint,
Frontend-Badge/Filter und MkDocs-Dokumentation.

- Migration 079: evidence_type VARCHAR(20) + Index
- Backend: Filter, Backfill-Endpoint mit Domain-Heuristik, CRUD
- Frontend: EvidenceTypeBadge (sky/amber/violet), Nachweisart-Dropdown
- Proxy: evidence_type Passthrough fuer controls + controls-count
- Tests: 22 Tests fuer Klassifikations-Heuristik
- Docs: Eigenes MkDocs-Kapitel mit Mermaid-Diagramm

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

admin-compliance/app/api/sdk/v1/canonical/route.ts

@@ -26,7 +26,7 @@ export async function GET(request: NextRequest) {
 
       case 'controls': {
         const controlParams = new URLSearchParams()
-        const passthrough = ['severity', 'domain', 'release_state', 'verification_method', 'category',
+        const passthrough = ['severity', 'domain', 'release_state', 'verification_method', 'category', 'evidence_type',
           'target_audience', 'source', 'search', 'control_type', 'exclude_duplicates', 'sort', 'order', 'limit', 'offset']
         for (const key of passthrough) {
           const val = searchParams.get(key)
@@ -39,7 +39,7 @@ export async function GET(request: NextRequest) {
 
       case 'controls-count': {
         const countParams = new URLSearchParams()
-        const countPassthrough = ['severity', 'domain', 'release_state', 'verification_method', 'category',
+        const countPassthrough = ['severity', 'domain', 'release_state', 'verification_method', 'category', 'evidence_type',
           'target_audience', 'source', 'search', 'control_type', 'exclude_duplicates']
         for (const key of countPassthrough) {
           const val = searchParams.get(key)