fix: safe area and UI polish pass

- Enable dark navigation headers in Tab navigator (fixes status bar overlap
  on all 5 tab screens automatically)
- Use useSafeAreaInsets for AlbumDetail/ArtistDetail back buttons
- Use useSafeAreaInsets for NowPlaying header and bottom padding
- Remove redundant paddingTop from Home heading and Login content
- Cleaner tab bar (height 60, better label spacing)

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

mobile/App.js

@@ -50,17 +50,32 @@ function HomeTabs() {
   return (
     <Tab.Navigator
       screenOptions={({ route }) => ({
-        headerShown: false,
-        tabBarStyle: { backgroundColor: '#1e1e1e', borderTopColor: '#2a2a2a' },
+        headerStyle: {
+          backgroundColor: '#121212',
+          elevation: 0,
+          shadowOpacity: 0,
+          borderBottomWidth: 0,
+        },
+        headerTintColor: '#fff',
+        headerTitleStyle: { fontWeight: '800', fontSize: 20 },
+        tabBarStyle: {
+          backgroundColor: '#1a1a1a',
+          borderTopColor: '#2a2a2a',
+          borderTopWidth: 1,
+          height: 60,
+          paddingBottom: 8,
+          paddingTop: 4,
+        },
         tabBarActiveTintColor: '#1db954',
-        tabBarInactiveTintColor: '#888',
+        tabBarInactiveTintColor: '#666',
+        tabBarLabelStyle: { fontSize: 10, fontWeight: '600', marginTop: 2 },
         tabBarIcon: ({ color, size }) => {
           const icons = { Home: 'home', Artists: 'person', Albums: 'disc', Search: 'search', Settings: 'settings-outline' };
-          return <Ionicons name={icons[route.name] || 'ellipse'} size={size} color={color} />;
+          return <Ionicons name={icons[route.name] || 'ellipse'} size={22} color={color} />;
         },
       })}
     >
-      <Tab.Screen name="Home"     component={HomeScreen}    options={{ title: 'Start' }} />
+      <Tab.Screen name="Home"     component={HomeScreen}    options={{ title: 'Start',          headerTitle: 'NovaSonic' }} />
       <Tab.Screen name="Artists"  component={ArtistsScreen} options={{ title: 'Künstler' }} />
       <Tab.Screen name="Albums"   component={AlbumsScreen}  options={{ title: 'Alben' }} />
       <Tab.Screen name="Search"   component={SearchScreen}  options={{ title: 'Suche' }} />