Add Authentik sign-in, fix tab scroll insets, and polish multi-account auth.

Mobile app detects SSO per server, supports OAuth sign-in, and preserves saved
sessions when adding accounts. Tab screens get proper chrome layout and tab-bar
clearance with scrollable page headers.

Co-authored-by: Cursor <cursoragent@cursor.com>

components/AuthServerPicker.tsx

@@ -18,6 +18,8 @@ import {
 
 type AuthServerPickerProps = {
   onReadyChange?: (ready: boolean) => void;
+  /** When true, picker sits inside the auth card with no outer margin. */
+  embedded?: boolean;
 };
 
 function modeSummary(mode: ServerMode, selfHostedUrl: string) {
@@ -26,7 +28,7 @@ function modeSummary(mode: ServerMode, selfHostedUrl: string) {
   return host || "Self-hosted";
 }
 
-export function AuthServerPicker({ onReadyChange }: AuthServerPickerProps) {
+export function AuthServerPicker({ onReadyChange, embedded = false }: AuthServerPickerProps) {
   const { colors } = useAppTheme();
   const { apiUrl, setInstanceUrl } = useAccounts();
   const [expanded, setExpanded] = useState(false);
@@ -93,7 +95,7 @@ export function AuthServerPicker({ onReadyChange }: AuthServerPickerProps) {
   }
 
   return (
-    <View style={styles.wrapper}>
+    <View style={[styles.wrapper, embedded && styles.wrapperEmbedded]}>
       <Pressable
         accessibilityRole="button"
         accessibilityState={{ expanded }}
@@ -182,6 +184,9 @@ const styles = StyleSheet.create({
     gap: spacing.sm,
     marginBottom: spacing.md,
   },
+  wrapperEmbedded: {
+    marginBottom: 0,
+  },
   trigger: {
     flexDirection: "row",
     alignItems: "center",