feat(profile): useDemographics hook + page-reload re-hydration

User-Bug: Demographics werden korrekt gespeichert (DB verified), aber nach
Page-Reload sah User leere Felder → dachte save kaputt. Root: kein GET-endpoint
+ kein server-state-rehydrate nach PATCH.

- hooks/useProfileData.ts: useDemographics() wraps useFetchOnce<DemographicsResponse>
  ('/api/profile/me/demographics'), splittet in fields + meta (consentAt/withdrawnAt)
- app/profile/index.tsx: serverDemographics ?? EMPTY_DEMOGRAPHICS const statt local
  state. Nach PATCH/DELETE: reloadDemographics() pulled fresh server data.

Edge-cases:
- 404 (endpoint nicht live) → fallback EMPTY, kein crash
- loading → EMPTY initial bis fetch resolved, konsistent mit other hooks
- withdrawnAt set → demoComplete=false (Demographics-Hint sichtbar trotz potentiell
  noch befüllter felder durch race-condition)

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

apps/rebreak-native/app/profile/index.tsx

@@ -18,6 +18,7 @@ import {
   useApprovedDomains,
   useCooldownHistory,
   useSosInsights,
+  useDemographics,
 } from '../../hooks/useProfileData';
 import { apiFetch } from '../../lib/api';
 
@@ -84,7 +85,6 @@ function mapHelpedBy(helpedBy: {
 export default function ProfileScreen() {
   const insets = useSafeAreaInsets();
   const [bannerDismissed, setBannerDismissed] = useState(false);
-  const [demographics, setDemographics] = useState<Demographics>(EMPTY_DEMOGRAPHICS);
   const [demographicsExpanded, setDemographicsExpanded] = useState(false);
   const { me } = useMe();
   const { user } = useAuthStore();
@@ -93,6 +93,13 @@ export default function ProfileScreen() {
   const { domains: approvedDomainsData } = useApprovedDomains();
   const { cooldownHistory } = useCooldownHistory();
   const { sosInsights } = useSosInsights();
+  const {
+    demographics: serverDemographics,
+    withdrawnAt,
+    reload: reloadDemographics,
+  } = useDemographics();
+
+  const demographics: Demographics = serverDemographics ?? EMPTY_DEMOGRAPHICS;
 
   const scrollViewRef = useRef<ScrollView | null>(null);
   const demographicsAnchorRef = useRef<View | null>(null);
@@ -117,7 +124,7 @@ export default function ProfileScreen() {
   const streakStartDate = formatStreakStartDate(me?.created_at);
 
   const showDigaBanner = currentStreak >= 30 && !bannerDismissed;
-  const demoComplete = isDemographicsComplete(demographics);
+  const demoComplete = !withdrawnAt && isDemographicsComplete(demographics);
 
   function scrollToDemographics() {
     const node = demographicsAnchorRef.current;
@@ -230,12 +237,12 @@ export default function ProfileScreen() {
             plan={profile.plan}
             expanded={demographicsExpanded}
             onChange={async (next) => {
-              setDemographics(next);
               try {
                 const result = await apiFetch<{ trialAwarded: boolean; expiresAt: string | null }>(
                   '/api/profile/me/demographics',
                   { method: 'PATCH', body: next },
                 );
+                reloadDemographics();
                 if (result.trialAwarded) {
                   Alert.alert(
                     'Pro-Woche freigeschaltet',
@@ -243,7 +250,7 @@ export default function ProfileScreen() {
                   );
                 }
               } catch {
-                // write failed — local state still updated optimistically
+                // write failed — optimistic update not applied, server state preserved
               }
             }}
             onRevokeConsent={() => {
@@ -256,8 +263,9 @@ export default function ProfileScreen() {
                     text: 'Loschen',
                     style: 'destructive',
                     onPress: () => {
-                      apiFetch('/api/profile/me/demographics', { method: 'DELETE' }).catch(() => {});
-                      setDemographics(EMPTY_DEMOGRAPHICS);
+                      apiFetch('/api/profile/me/demographics', { method: 'DELETE' })
+                        .then(() => reloadDemographics())
+                        .catch(() => {});
                     },
                   },
                 ],

apps/rebreak-native/hooks/useProfileData.ts

@@ -141,3 +141,49 @@ export function useSosInsights() {
   return { sosInsights: data, loading, error, reload };
 }
 
+export type Demographics = {
+  birthYear: number | null;
+  gender: string | null;
+  maritalStatus: string | null;
+  employmentStatus: string | null;
+  shiftWork: boolean | null;
+  industry: string | null;
+  jobTenure: string | null;
+  bundesland: string | null;
+  city: string | null;
+};
+
+type DemographicsResponse = Demographics & {
+  consentAt: string | null;
+  withdrawnAt: string | null;
+};
+
+export function useDemographics() {
+  const { data, loading, error, reload } = useFetchOnce<DemographicsResponse>(
+    '/api/profile/me/demographics',
+  );
+
+  const demographics: Demographics | null = data
+    ? {
+        birthYear: data.birthYear,
+        gender: data.gender,
+        maritalStatus: data.maritalStatus,
+        employmentStatus: data.employmentStatus,
+        shiftWork: data.shiftWork,
+        industry: data.industry,
+        jobTenure: data.jobTenure,
+        bundesland: data.bundesland,
+        city: data.city,
+      }
+    : null;
+
+  return {
+    demographics,
+    consentAt: data?.consentAt ?? null,
+    withdrawnAt: data?.withdrawnAt ?? null,
+    loading,
+    error,
+    reload,
+  };
+}
+