refactor(settings): drill-down navigation replacing tabbed layout (#605)

* refactor(settings): drill-down navigation replacing tabbed layout

Replaces the 4-tab settings layout with a native Android-style drill-down:
a single category list (SettingsScreen) where each row pushes a dedicated
sub-page onto the Navigation3 back stack (SettingsConnection / Appearance /
Chat / NavBar / Behavior / About). Each sub-page is its own NavKey destination
registered in Navigation.kt and reuses the existing section composables.

- SettingsScreen becomes the category list with icon + label + summary
  (Appearance row shows live theme + language, e.g. "Dark · 한국어").
- New SettingsSubPages.kt hosts the 6 full-screen sub-pages.
- AboutSection promoted out of SettingsScreen into its own sub-page.
- SettingsViewModel remains the single source of truth; no persistence changes.
- Adds settings_summary_* strings for list subtitles.

Consumes the in-app language switcher from the prior commit (AppearancePage
passes appLanguage through to AppearanceSection).

* [bug] fix settings sub-page back button opening drawer on first tap

The ModalNavigationDrawer wraps the whole app and stays gesture-enabled on
the Settings root (a DRAWER_GESTURE_SCREEN). Drilling into a sub-page
(SettingsConnection/Appearance/Chat/NavBar/Behavior/About) disables gestures,
but the existing LaunchedEffect only snapped the drawer closed when it was
already isOpen. The drawer's scrim surface lingered during the transition and
intercepted the first back-button tap, sliding the sidebar open instead of
navigating back.

Now snapTo(Closed) unconditionally whenever gestures are disabled — a safe
no-op when already closed — so the sub-page back button works on the first tap.

* [bug] fix settings sub-page back button opening drawer (gesture-surface race)

The first "back" tap on a settings sub-page opened the sidebar instead of
navigating back. Root cause: Settings root is a gesture-enabled drawer screen,
and the sub-pages are the first destinations ever drilled down from it. When
navigating in, ModalNavigationDrawer's gesture interceptor surface lingered
for a frame (gesture -> non-gesture transition), so the top-left tap was
consumed by the drawer instead of the Back IconButton. The previous snapTo
fix only reset drawer *state*, not the gesture layer, so it didn't help.

Fix: NavigationController now holds a closeDrawer hook (set by MainNavigation)
and invokes it synchronously inside navigateTo() when pushing a non-primary
sub-page. The drawer is dismissed in the same tap handler that triggers the
navigation, before any recomposition, so the sub-page is never tappable while
the gesture surface is still mounted. The LaunchedEffect(gesturesEnabled)
snapTo remains as a backstop for non-navigateTo entries.

* fix(#603): delay drawer gesture activation to prevent residual swipe

* fix(#603): fix settings back navigation and drawer auto-open

---------

Co-authored-by: hy4ri <hy4ri@users.noreply.github.com>

app/src/main/java/com/m57/hermescontrol/NavigationKeys.kt

@@ -54,3 +54,17 @@ import kotlinx.serialization.Serializable
 @Serializable data object ProvidersScreen : NavKey
 
 @Serializable data object AnalyticsScreen : NavKey
+
+// ── Settings drill-down sub-pages ──────────────────────────────────────
+
+@Serializable data object SettingsConnection : NavKey
+
+@Serializable data object SettingsAppearance : NavKey
+
+@Serializable data object SettingsChat : NavKey
+
+@Serializable data object SettingsNavBar : NavKey
+
+@Serializable data object SettingsBehavior : NavKey
+
+@Serializable data object SettingsAbout : NavKey