fix: Faceted Counts — NULL-Werte einbeziehen + AbortController fuer Race Conditions

Backend: Facets zaehlen jetzt Controls OHNE Wert (z.B. "Ohne Nachweis")
als __none__. Filter unterstuetzen __none__ fuer verification_method,
category, evidence_type. Counts addieren sich immer zum Total.

Frontend: "Ohne X" Optionen in Dropdowns. AbortController verhindert
dass aeltere API-Antworten neuere ueberschreiben.

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

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

@@ -101,6 +101,10 @@ export default function ControlLibraryPage() {
     similarity_score: number; match_rank: number; match_method: string
   }>>([])
 
+  // Abort controllers for cancelling stale requests
+  const metaAbortRef = useRef<AbortController | null>(null)
+  const controlsAbortRef = useRef<AbortController | null>(null)
+
   // Debounce search
   const searchTimer = useRef<ReturnType<typeof setTimeout> | null>(null)
   useEffect(() => {
@@ -135,17 +139,25 @@ export default function ControlLibraryPage() {
     } catch { /* ignore */ }
   }, [])
 
-  // Load faceted metadata (reloads when filters change)
+  // Load faceted metadata (reloads when filters change, cancels stale requests)
   const loadMeta = useCallback(async () => {
+    if (metaAbortRef.current) metaAbortRef.current.abort()
+    const controller = new AbortController()
+    metaAbortRef.current = controller
     try {
       const qs = buildParams()
-      const res = await fetch(`${BACKEND_URL}?endpoint=controls-meta${qs ? `&${qs}` : ''}`)
-      if (res.ok) setMeta(await res.json())
-    } catch { /* ignore */ }
+      const res = await fetch(`${BACKEND_URL}?endpoint=controls-meta${qs ? `&${qs}` : ''}`, { signal: controller.signal })
+      if (res.ok && !controller.signal.aborted) setMeta(await res.json())
+    } catch (e) {
+      if (e instanceof DOMException && e.name === 'AbortError') return
+    }
   }, [buildParams])
 
-  // Load controls page
+  // Load controls page (cancels stale requests)
   const loadControls = useCallback(async () => {
+    if (controlsAbortRef.current) controlsAbortRef.current.abort()
+    const controller = new AbortController()
+    controlsAbortRef.current = controller
     try {
       setLoading(true)
 
@@ -164,19 +176,22 @@ export default function ControlLibraryPage() {
       const countQs = buildParams()
 
       const [ctrlRes, countRes] = await Promise.all([
-        fetch(`${BACKEND_URL}?endpoint=controls&${qs}`),
-        fetch(`${BACKEND_URL}?endpoint=controls-count&${countQs}`),
+        fetch(`${BACKEND_URL}?endpoint=controls&${qs}`, { signal: controller.signal }),
+        fetch(`${BACKEND_URL}?endpoint=controls-count&${countQs}`, { signal: controller.signal }),
       ])
 
-      if (ctrlRes.ok) setControls(await ctrlRes.json())
-      if (countRes.ok) {
-        const data = await countRes.json()
-        setTotalCount(data.total || 0)
+      if (!controller.signal.aborted) {
+        if (ctrlRes.ok) setControls(await ctrlRes.json())
+        if (countRes.ok) {
+          const data = await countRes.json()
+          setTotalCount(data.total || 0)
+        }
       }
     } catch (err) {
+      if (err instanceof DOMException && err.name === 'AbortError') return
       setError(err instanceof Error ? err.message : 'Fehler beim Laden')
     } finally {
-      setLoading(false)
+      if (!controller.signal.aborted) setLoading(false)
     }
   }, [buildParams, sortBy, currentPage])
 
@@ -701,6 +716,7 @@ export default function ControlLibraryPage() {
               {Object.entries(VERIFICATION_METHODS).map(([k, v]) => (
                 <option key={k} value={k}>{v.label}{meta?.verification_method_counts?.[k] ? ` (${meta.verification_method_counts[k]})` : ''}</option>
               ))}
+              {meta?.verification_method_counts?.['__none__'] ? <option value="__none__">Ohne Nachweis ({meta.verification_method_counts['__none__']})</option> : null}
             </select>
             <select
               value={categoryFilter}
@@ -711,6 +727,7 @@ export default function ControlLibraryPage() {
               {CATEGORY_OPTIONS.map(c => (
                 <option key={c.value} value={c.value}>{c.label}{meta?.category_counts?.[c.value] ? ` (${meta.category_counts[c.value]})` : ''}</option>
               ))}
+              {meta?.category_counts?.['__none__'] ? <option value="__none__">Ohne Kategorie ({meta.category_counts['__none__']})</option> : null}
             </select>
             <select
               value={evidenceTypeFilter}
@@ -721,6 +738,7 @@ export default function ControlLibraryPage() {
               {EVIDENCE_TYPE_OPTIONS.map(c => (
                 <option key={c.value} value={c.value}>{c.label}{meta?.evidence_type_counts?.[c.value] ? ` (${meta.evidence_type_counts[c.value]})` : ''}</option>
               ))}
+              {meta?.evidence_type_counts?.['__none__'] ? <option value="__none__">Ohne Nachweisart ({meta.evidence_type_counts['__none__']})</option> : null}
             </select>
             <select
               value={audienceFilter}