feat(ui): Backend-Modal — Domains zum Backend zuweisen

Symmetrisch zur Backend-Auswahl im Domain-Modal: das Backend-Modal
hat jetzt einen Multi-Select für Domains. Auswahl wird beim Speichern
gegen den aktuellen Stand diff't und in N parallele PUTs an
/domains/:id übersetzt — Add setzt primary_backend_id auf die ID,
Remove auf null.

Domain bleibt die Quelle der Wahrheit (kein Schema-Change). Die
Backend-Seite ist nur eine alternative Edit-Affordance.

Version 1.0.7.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

management-ui/src/components/Layout/Sidebar.tsx

@@ -68,7 +68,7 @@ const NAV: NavSection[] = [
   },
 ]
 
-const VERSION = '1.0.6'
+const VERSION = '1.0.7'
 
 export default function Sidebar({ isOpen, onClose }: SidebarProps) {
   const { t } = useTranslation()

management-ui/src/i18n/locales/de/common.json

@@ -207,6 +207,9 @@
     "active": "Aktiv",
     "usedBy": "Genutzt von",
     "noDomain": "keine Domain",
+    "attachedDomains": "Domains",
+    "attachedDomainsHint": "Domains, die dieses Backend als Primary verwenden. Auswahl umkonfiguriert die Domains direkt — gleiche Quelle wie der Backend-Picker im Domain-Modal.",
+    "selectDomains": "Domains wählen",
     "actions": "Aktionen",
     "deleteConfirm": "Backend {{name}} wirklich löschen?"
   },

management-ui/src/i18n/locales/en/common.json

@@ -207,6 +207,9 @@
     "active": "Active",
     "usedBy": "Used by",
     "noDomain": "no domain",
+    "attachedDomains": "Domains",
+    "attachedDomainsHint": "Domains that use this backend as their primary. Selecting domains here reconfigures them directly — same source of truth as the Domain modal's backend picker.",
+    "selectDomains": "Select domains",
     "actions": "Actions",
     "deleteConfirm": "Really delete backend {{name}}?"
   },

management-ui/src/pages/Backends/index.tsx

@@ -26,6 +26,7 @@ interface BackendFormValues {
   port: number
   health_check_path?: string
   active: boolean
+  domain_ids?: number[]
 }
 
 async function listBackends(): Promise<Backend[]> {
@@ -35,16 +36,25 @@ async function listBackends(): Promise<Backend[]> {
   return payload.backends ?? []
 }
 
-interface DomainLite {
+// DomainFull mirrors the API contract; we need the full body to PUT
+// the domain back when re-attaching/detaching it (the handler does
+// a full-row replace, not a patch). Fields beyond what the form
+// shows are passed through verbatim.
+interface DomainFull {
   id: number
   name: string
   active: boolean
   primary_backend_id?: number | null
+  http_to_https: boolean
+  hsts_enabled: boolean
+  notes?: string | null
+  created_at?: string
+  updated_at?: string
 }
-async function listDomains(): Promise<DomainLite[]> {
+async function listDomains(): Promise<DomainFull[]> {
   const r = await apiClient.get('/domains')
   if (!isEnvelope(r.data)) return []
-  return (r.data.data as { domains?: DomainLite[] }).domains ?? []
+  return (r.data.data as { domains?: DomainFull[] }).domains ?? []
 }
 
 export default function BackendsPage() {
@@ -65,27 +75,72 @@ export default function BackendsPage() {
   const [creating, setCreating] = useState(false)
   const [form] = Form.useForm<BackendFormValues>()
 
+  // syncDomainAttachments diff-applies the multi-select to the
+  // domains table — domains that should now point at this backend
+  // get a PUT with primary_backend_id=backend.id; domains that used
+  // to point at it but were unchecked get a PUT with null.
+  // Domains are kept canonical in their own table; this is just the
+  // reverse-edit affordance the operator asked for.
+  async function syncDomainAttachments(backendID: number, selected: number[]) {
+    const all = domains ?? []
+    const wasAttached = new Set(all.filter(d => d.primary_backend_id === backendID).map(d => d.id))
+    const want = new Set(selected)
+    const adds = [...want].filter(id => !wasAttached.has(id))
+    const removes = [...wasAttached].filter(id => !want.has(id))
+
+    const puts: Promise<unknown>[] = []
+    for (const id of adds) {
+      const d = all.find(x => x.id === id)
+      if (!d) continue
+      puts.push(apiClient.put(`/domains/${id}`, {
+        name: d.name, active: d.active,
+        http_to_https: d.http_to_https, hsts_enabled: d.hsts_enabled,
+        notes: d.notes ?? '', primary_backend_id: backendID,
+      }))
+    }
+    for (const id of removes) {
+      const d = all.find(x => x.id === id)
+      if (!d) continue
+      puts.push(apiClient.put(`/domains/${id}`, {
+        name: d.name, active: d.active,
+        http_to_https: d.http_to_https, hsts_enabled: d.hsts_enabled,
+        notes: d.notes ?? '', primary_backend_id: null,
+      }))
+    }
+    if (puts.length > 0) await Promise.all(puts)
+  }
+
   const create = useMutation({
     mutationFn: async (v: BackendFormValues) => {
-      await apiClient.post('/backends', v)
+      const { domain_ids, ...body } = v
+      const r = await apiClient.post('/backends', body)
+      const env = r.data
+      const created = isEnvelope(env) ? (env.data as Backend) : null
+      if (created && domain_ids && domain_ids.length > 0) {
+        await syncDomainAttachments(created.id, domain_ids)
+      }
     },
     onSuccess: () => {
       message.success(t('common.save'))
       setCreating(false)
       form.resetFields()
       void qc.invalidateQueries({ queryKey: ['backends'] })
+      void qc.invalidateQueries({ queryKey: ['domains'] })
     },
   })
 
   const update = useMutation({
     mutationFn: async ({ id, v }: { id: number; v: BackendFormValues }) => {
-      await apiClient.put(`/backends/${id}`, v)
+      const { domain_ids, ...body } = v
+      await apiClient.put(`/backends/${id}`, body)
+      await syncDomainAttachments(id, domain_ids ?? [])
     },
     onSuccess: () => {
       message.success(t('common.save'))
       setEditing(null)
       form.resetFields()
       void qc.invalidateQueries({ queryKey: ['backends'] })
+      void qc.invalidateQueries({ queryKey: ['domains'] })
     },
   })
 
@@ -124,6 +179,7 @@ export default function BackendsPage() {
               port: row.port,
               health_check_path: row.health_check_path ?? undefined,
               active: row.active,
+              domain_ids: domainsForBackend(row.id).map(d => d.id),
             })
           }}>{t('common.edit')}</Button>
           <Popconfirm
@@ -181,6 +237,25 @@ export default function BackendsPage() {
           <Form.Item label={t('backends.active')} name="active" valuePropName="checked">
             <Switch />
           </Form.Item>
+          <Form.Item
+            label={t('backends.attachedDomains')}
+            name="domain_ids"
+            extra={t('backends.attachedDomainsHint')}
+          >
+            <Select
+              mode="multiple"
+              allowClear
+              showSearch
+              optionFilterProp="label"
+              placeholder={t('backends.selectDomains')}
+              options={(domains ?? []).map(d => ({
+                value: d.id,
+                label: d.primary_backend_id && d.primary_backend_id !== editing?.id
+                  ? `${d.name} (zur Zeit: #${d.primary_backend_id})`
+                  : d.name,
+              }))}
+            />
+          </Form.Item>
         </Form>
       </Modal>
     </div>