fix(mobile): replace 404 media library error with session-required state and device gallery fallback

The Postiz public API v1 does not expose a media listing endpoint.
Switch URL to the correct internal path (/media?page=0&search=), handle
the resulting 401 with a dedicated lock-icon state, and wire the existing
device gallery picker as an onPickFromDevice fallback so the modal stays
usable.

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

artifacts/postiz-mobile/app/(tabs)/compose.tsx

@@ -767,6 +767,7 @@ export default function ComposeScreen() {
         workspaces={workspaces}
         maxSelect={MAX_IMAGES - mediaItems.length}
         onClose={() => setShowMediaLibrary(false)}
+        onPickFromDevice={() => { setShowMediaLibrary(false); pickImage(); }}
         onSelect={(items: LibraryMediaItem[]) => {
           setMediaItems((prev) =>
             [

artifacts/postiz-mobile/components/MediaLibraryModal.tsx

@@ -35,6 +35,7 @@ interface Props {
   maxSelect: number;
   onClose: () => void;
   onSelect: (items: LibraryMediaItem[]) => void;
+  onPickFromDevice?: () => void;
 }
 
 function resolveUrl(path: string, baseUrl: string): string {
@@ -43,7 +44,7 @@ function resolveUrl(path: string, baseUrl: string): string {
   return `${origin}/${path.replace(/^\//, "")}`;
 }
 
-export function MediaLibraryModal({ visible, workspaces, defaultWorkspaceId, maxSelect, onClose, onSelect }: Props) {
+export function MediaLibraryModal({ visible, workspaces, defaultWorkspaceId, maxSelect, onClose, onSelect, onPickFromDevice }: Props) {
   const colors = useColors();
   const insets = useSafeAreaInsets();
   const [activeId, setActiveId] = useState<string>("");
@@ -66,17 +67,19 @@ export function MediaLibraryModal({ visible, workspaces, defaultWorkspaceId, max
     if (!activeWorkspace) return;
     setLoading(true);
     setError(null);
-    const url = `${activeWorkspace.baseUrl}/media`;
+    const apiBase = activeWorkspace.baseUrl.replace(/\/public\/v1$/, "");
+    const url = `${apiBase}/media?page=0&search=`;
     try {
       // eslint-disable-next-line no-undef
       const res = await globalThis.fetch(url, {
         headers: { Authorization: activeWorkspace.apiKey },
       });
       if (!res.ok) {
+        if (res.status === 401 || res.status === 403) {
+          throw new Error("SESSION_REQUIRED");
+        }
         if (res.status === 404) {
-          throw new Error(
+          throw new Error("ENDPOINT_NOT_FOUND");
-            `Media listing endpoint not found (404).\nURL tried: ${url}\n\nThis feature requires Postiz to expose GET /media in its public API. Your version may not support it yet.`
-          );
         }
         throw new Error(`HTTP ${res.status} — ${url}`);
       }
@@ -171,6 +174,29 @@ export function MediaLibraryModal({ visible, workspaces, defaultWorkspaceId, max
           <View style={styles.centered}>
             <ActivityIndicator color={colors.primary} size="large" />
           </View>
+        ) : error === "SESSION_REQUIRED" ? (
+          <View style={styles.centered}>
+            <Feather name="lock" size={28} color={colors.mutedForeground} />
+            <Text style={[styles.errorText, { color: colors.mutedForeground }]}>
+              {"Media library requires a web session.\nAPI key access is not supported by Postiz."}
+            </Text>
+            {onPickFromDevice && (
+              <TouchableOpacity
+                onPress={() => { onClose(); onPickFromDevice(); }}
+                style={[styles.retryBtn, { backgroundColor: colors.primary }]}
+                activeOpacity={0.8}
+              >
+                <Text style={[styles.retryText, { color: colors.primaryForeground }]}>Use device gallery</Text>
+              </TouchableOpacity>
+            )}
+          </View>
+        ) : error === "ENDPOINT_NOT_FOUND" ? (
+          <View style={styles.centered}>
+            <Feather name="slash" size={28} color={colors.mutedForeground} />
+            <Text style={[styles.errorText, { color: colors.mutedForeground }]}>
+              {"Media library endpoint not found on this server."}
+            </Text>
+          </View>
         ) : error ? (
           <View style={styles.centered}>
             <Feather name="alert-circle" size={28} color={colors.error} />