feat: Faceted Search — Dropdown-Counts passen sich aktiven Filtern an

Backend: controls-meta akzeptiert alle Filter-Parameter und berechnet
Faceted Counts (jede Dimension zaehlt mit allen ANDEREN Filtern).
Neue Facets: severity, verification_method, category, evidence_type,
release_state — zusaetzlich zu domains, sources, type_counts.

Frontend: loadMeta laedt bei jeder Filteraenderung neu, alle Dropdowns
zeigen kontextsensitive Zahlen. Proxy leitet Filter an controls-meta weiter.

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

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

@@ -50,9 +50,18 @@ export async function GET(request: NextRequest) {
         break
       }
 
-      case 'controls-meta':
-        backendPath = '/api/compliance/v1/canonical/controls-meta'
+      case 'controls-meta': {
+        const metaParams = new URLSearchParams()
+        const metaPassthrough = ['severity', 'domain', 'release_state', 'verification_method', 'category', 'evidence_type',
+          'target_audience', 'source', 'search', 'control_type', 'exclude_duplicates']
+        for (const key of metaPassthrough) {
+          const val = searchParams.get(key)
+          if (val) metaParams.set(key, val)
+        }
+        const metaQs = metaParams.toString()
+        backendPath = `/api/compliance/v1/canonical/controls-meta${metaQs ? `?${metaQs}` : ''}`
         break
+      }
 
       case 'control': {
         const controlId = searchParams.get('id')