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/widgets/settings/settings_appearance.dart

@@ -51,6 +51,18 @@ class SettingsAppearanceSection extends StatelessWidget {
           children: [
             _ThemeRow(settings: settings),
             _BottomBarStyleRow(settings: settings),
+            NooSettingsRow(
+              icon: LucideIcons.search,
+              label: const Text('Search in bottom bar'),
+              subtitle: const Text(
+                'Adds Search to the bottom bar and removes it from the top '
+                'bar - leaves room for one fewer regular tab',
+              ),
+              trailing: NooToggle(
+                checked: settings.searchInBottomBar,
+                onChanged: settings.setSearchInBottomBar,
+              ),
+            ),
           ],
         ),
         const SizedBox(height: NooSpace.xl),