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/TabPage.tsx

@@ -1,7 +1,6 @@
 import type { ReactNode } from "react";
 import { StyleSheet, View } from "react-native";
 import { StatusBar } from "expo-status-bar";
-import { useSafeAreaInsets } from "react-native-safe-area-context";
 
 import { TopChromeBar } from "@/components/TopChromeBar";
 import { useAppTheme } from "@/contexts/ThemeContext";
@@ -10,23 +9,15 @@ type TabPageProps = {
   children: ReactNode;
 };
 
-/** Tab root — floating blurred top chrome; children should be a TabScrollView. */
+/** Tab root — pinned top chrome, scrollable body below. */
 export function TabPage({ children }: TabPageProps) {
-  const insets = useSafeAreaInsets();
   const { isDark } = useAppTheme();
 
   return (
     <View style={styles.root}>
       <StatusBar style={isDark ? "light" : "dark"} />
-      <View
-        style={[
-          styles.content,
-          { paddingLeft: insets.left, paddingRight: insets.right },
-        ]}
-      >
-        {children}
-      </View>
       <TopChromeBar />
+      <View style={styles.content}>{children}</View>
     </View>
   );
 }
@@ -38,6 +29,7 @@ const styles = StyleSheet.create({
   },
   content: {
     flex: 1,
+    minHeight: 0,
     backgroundColor: "transparent",
   },
 });