feat(control-library): add document source dropdown filter

Add "Dokumentenursprung" filter dropdown to the control library page.
Extracts unique source_citation.source values from controls, sorted by
frequency. Includes "Ohne Quelle" option for controls without source info.

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

admin-compliance/app/sdk/control-library/page.tsx

@@ -34,6 +34,7 @@ export default function ControlLibraryPage() {
   const [verificationFilter, setVerificationFilter] = useState<string>('')
   const [categoryFilter, setCategoryFilter] = useState<string>('')
   const [audienceFilter, setAudienceFilter] = useState<string>('')
+  const [sourceFilter, setSourceFilter] = useState<string>('')
 
   // CRUD state
   const [mode, setMode] = useState<'list' | 'detail' | 'create' | 'edit'>('list')
@@ -78,6 +79,22 @@ export default function ControlLibraryPage() {
     return Array.from(set).sort()
   }, [controls])
 
+  // Derived: unique document sources (sorted by frequency)
+  const documentSources = useMemo(() => {
+    const counts = new Map<string, number>()
+    let noSource = 0
+    for (const c of controls) {
+      const src = c.source_citation?.source
+      if (src) {
+        counts.set(src, (counts.get(src) || 0) + 1)
+      } else {
+        noSource++
+      }
+    }
+    const sorted = Array.from(counts.entries()).sort((a, b) => b[1] - a[1])
+    return { sources: sorted, noSourceCount: noSource }
+  }, [controls])
+
   // Filtered controls
   const filteredControls = useMemo(() => {
     return controls.filter(c => {
@@ -87,6 +104,14 @@ export default function ControlLibraryPage() {
       if (verificationFilter && c.verification_method !== verificationFilter) return false
       if (categoryFilter && c.category !== categoryFilter) return false
       if (audienceFilter && c.target_audience !== audienceFilter) return false
+      if (sourceFilter) {
+        const src = c.source_citation?.source || ''
+        if (sourceFilter === '__none__') {
+          if (src) return false
+        } else {
+          if (src !== sourceFilter) return false
+        }
+      }
       if (searchQuery) {
         const q = searchQuery.toLowerCase()
         return (
@@ -98,10 +123,10 @@ export default function ControlLibraryPage() {
       }
       return true
     })
-  }, [controls, severityFilter, domainFilter, stateFilter, verificationFilter, categoryFilter, audienceFilter, searchQuery])
+  }, [controls, severityFilter, domainFilter, stateFilter, verificationFilter, categoryFilter, audienceFilter, sourceFilter, searchQuery])
 
   // Reset page when filters change
-  useEffect(() => { setCurrentPage(1) }, [severityFilter, domainFilter, stateFilter, verificationFilter, categoryFilter, audienceFilter, searchQuery])
+  useEffect(() => { setCurrentPage(1) }, [severityFilter, domainFilter, stateFilter, verificationFilter, categoryFilter, audienceFilter, sourceFilter, searchQuery])
 
   // Pagination
   const totalPages = Math.max(1, Math.ceil(filteredControls.length / PAGE_SIZE))
@@ -441,6 +466,17 @@ export default function ControlLibraryPage() {
                 <option key={k} value={k}>{v.label}</option>
               ))}
             </select>
+            <select
+              value={sourceFilter}
+              onChange={e => setSourceFilter(e.target.value)}
+              className="text-sm border border-gray-300 rounded-lg px-2 py-1.5 focus:outline-none focus:ring-2 focus:ring-purple-500 max-w-[220px]"
+            >
+              <option value="">Dokumentenursprung</option>
+              <option value="__none__">Ohne Quelle ({documentSources.noSourceCount})</option>
+              {documentSources.sources.map(([src, count]) => (
+                <option key={src} value={src}>{src} ({count})</option>
+              ))}
+            </select>
           </div>
         </div>