feat(ldap): per-user exclude/denylist filter for sync

Add a per-username denylist so individual accounts (service accounts like
administrator, krbtgt, guest, ldap$) can be excluded from LDAP sync,
independent of the group/OU include-filter which only scopes the search.

- schema: LdapConfig.userExcludeList String[] (+ migration)
- sync: skip excluded usernames (case-insensitive) before recording the DN,
  so an already-imported user added to the list gets deactivated next sync
- DTO / config service / controller / scheduler: thread userExcludeList through
- web: exclude-list admin UI section (add/remove/save) + de/en translations
- tests: 3 specs covering empty list, case-insensitive skip, deactivation

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/web/src/app/(portal)/admin/ldap/page.tsx

@@ -24,6 +24,7 @@ interface LdapConfig {
   syncIntervalMin: number;
   isActive: boolean;
   groupFilterDns: string[];
+  userExcludeList: string[];
   lastSyncAt: string | null;
   fieldMappings: FieldMapping[];
 }
@@ -83,6 +84,11 @@ export default function AdminLdapPage() {
   const [savingFilter, setSavingFilter] = useState(false);
   const [discoverSearch, setDiscoverSearch] = useState('');
 
+  // Per-user exclude/denylist (individual usernames never imported)
+  const [userExcludeList, setUserExcludeList] = useState<string[]>([]);
+  const [newExcludeUser, setNewExcludeUser] = useState('');
+  const [savingExclude, setSavingExclude] = useState(false);
+
   const filteredDiscovered = discovered?.filter((entry) => {
     const q = discoverSearch.trim().toLowerCase();
     if (!q) return true;
@@ -113,6 +119,7 @@ export default function AdminLdapPage() {
             isActive: data.isActive ?? true,
           });
           setGroupFilterDns(data.groupFilterDns ?? []);
+          setUserExcludeList(data.userExcludeList ?? []);
         }
       }
     } catch {
@@ -298,6 +305,36 @@ export default function AdminLdapPage() {
     }
   };
 
+  const handleAddExcludeUser = () => {
+    const name = newExcludeUser.trim().toLowerCase();
+    if (!name || userExcludeList.includes(name)) return;
+    setUserExcludeList((prev) => [...prev, name]);
+    setNewExcludeUser('');
+  };
+
+  const handleRemoveExcludeUser = (name: string) => {
+    setUserExcludeList((prev) => prev.filter((u) => u !== name));
+  };
+
+  const handleSaveExcludeList = async () => {
+    setSavingExclude(true);
+    try {
+      const res = await fetch(`${API_URL}/ldap/config`, {
+        method: 'PATCH',
+        headers: { 'Content-Type': 'application/json' },
+        credentials: 'include',
+        body: JSON.stringify({ userExcludeList }),
+      });
+      if (res.ok) {
+        await fetchConfig();
+      }
+    } catch {
+      // silently fail
+    } finally {
+      setSavingExclude(false);
+    }
+  };
+
   if (!hasAccess) {
     return (
       <div className="flex items-center justify-center min-h-[60vh]">
@@ -666,6 +703,82 @@ export default function AdminLdapPage() {
         </section>
       )}
 
+      {/* Section 2.6: Per-user exclude/denylist */}
+      {config && (
+        <section className="rounded-lg border border-border p-6">
+          <h2 className="text-lg font-semibold text-foreground mb-2">
+            {t('userExclude.title')}
+          </h2>
+          <p className="text-sm text-muted-foreground mb-4">
+            {t('userExclude.description')}
+          </p>
+
+          <div className="flex items-end gap-3 mb-4">
+            <div className="flex-1 space-y-1">
+              <label className="text-xs font-medium text-muted-foreground">
+                {t('userExclude.username')}
+              </label>
+              <input
+                type="text"
+                value={newExcludeUser}
+                onChange={(e) => setNewExcludeUser(e.target.value)}
+                onKeyDown={(e) => {
+                  if (e.key === 'Enter') {
+                    e.preventDefault();
+                    handleAddExcludeUser();
+                  }
+                }}
+                placeholder="administrator, krbtgt, guest, ldap$ ..."
+                className="flex h-9 w-full rounded-md border border-input bg-background px-3 py-1 text-sm font-mono"
+              />
+            </div>
+            <button
+              type="button"
+              onClick={handleAddExcludeUser}
+              className="h-9 rounded-md border border-border px-3 text-xs font-medium text-foreground hover:bg-muted transition-colors"
+            >
+              {t('userExclude.add')}
+            </button>
+          </div>
+
+          <div className="mb-4">
+            <p className="text-xs font-medium text-muted-foreground mb-2">
+              {t('userExclude.excluded')}
+            </p>
+            {userExcludeList.length === 0 ? (
+              <p className="text-sm text-muted-foreground">{t('userExclude.empty')}</p>
+            ) : (
+              <ul className="flex flex-wrap gap-2">
+                {userExcludeList.map((name) => (
+                  <li
+                    key={name}
+                    className="flex items-center gap-2 rounded-md border border-border px-3 py-1.5 text-sm"
+                  >
+                    <span className="font-mono text-xs text-foreground">{name}</span>
+                    <button
+                      type="button"
+                      onClick={() => handleRemoveExcludeUser(name)}
+                      className="shrink-0 rounded px-1.5 py-0.5 text-xs text-destructive hover:bg-destructive/10 transition-colors"
+                    >
+                      {t('fieldMapping.remove')}
+                    </button>
+                  </li>
+                ))}
+              </ul>
+            )}
+          </div>
+
+          <button
+            type="button"
+            onClick={handleSaveExcludeList}
+            disabled={savingExclude}
+            className="rounded-md bg-primary px-4 py-2 text-sm font-medium text-primary-foreground hover:opacity-90 transition-opacity disabled:opacity-50"
+          >
+            {savingExclude ? tCommon('loading') : t('userExclude.save')}
+          </button>
+        </section>
+      )}
+
       {/* Section 3: Sync Settings (D-14) */}
       {config && (
         <section className="rounded-lg border border-border p-6">