Add "Search in bottom bar" to Settings

New Settings > Appearance toggle moves Search into the bottom bar and
out of the top bar, so there's only one search entry point on screen.
Tapping it pushes SearchView same as before - it's never highlighted,
since it isn't a real destination.

- Attached: Search becomes the row's last item, styled like any other
  tab but permanently idle.
- Floating: Search gets its own separate, always fully round satellite
  circle beside the bar instead.

Enabling it costs one regular tab: SettingsController.maxVisibleTabs
is now a dynamic getter (defaultMaxVisibleTabs - 1 while the toggle is
on) instead of the old flat constant, re-enforced immediately if the
user already has all 5 slots filled - the same cleanup path used for
a fresh install or an app update that added a new tab.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

lib/main.dart

@@ -473,11 +473,20 @@ class _MainShellViewState extends State<MainShellView> {
     } else {
       final navStyle = NooLayout.navStyle(context);
       final bottomBarStyle = settings.bottomBarStyle;
+      // Picking/offline already override the tab set itself (see
+      // pinnedTabs above) - Search doesn't belong in either: there's
+      // nothing to search for a file-picking flow, and Search needs the
+      // network Offline mode doesn't have.
+      final showBottomBarSearch = !overrideActive && settings.searchInBottomBar;
       scaffold = Scaffold(
         backgroundColor: colors.bg,
         drawerScrimColor: colors.scrim,
         appBar: pickRequest == null
-            ? AppTopBar(style: navStyle, tab: selectedTab)
+            ? AppTopBar(
+                style: navStyle,
+                tab: selectedTab,
+                searchInBottomBar: showBottomBarSearch,
+              )
             : null,
         drawer: pickRequest == null ? const AppDrawer() : null,
         // Floating needs the body to draw behind the bar's own transparent
@@ -502,6 +511,7 @@ class _MainShellViewState extends State<MainShellView> {
           barStyle: bottomBarStyle,
           tabs: pinnedTabs,
           selectedIndex: pinnedIndex,
+          onSearchTap: showBottomBarSearch ? () => openSearch(context) : null,
           onDestinationSelected: (index) {
             final tappedTab = pinnedTabs[index];
             if (tappedTab == _currentTab) {