fix(ux): keep Settings highlighted in bottom nav on drill-down sub-pages (issue #637) (#643)

* fix(ux): keep Settings highlighted in bottom nav on drill-down sub-pages (issue #637)

Map Settings drill-down destinations (SettingsConnection, SettingsAppearance, SettingsChat, SettingsNavBar, SettingsBehavior, SettingsAbout) back to SettingsScreen for bottom-nav selection only - navigation is unaffected.

- Add selectedBottomNavDestination() helper in Navigation.kt
- Extract bar-height logic into Modifier.bottomNavigationHeight() (ICON_AND_TEXT now uses heightIn(min=80.dp) so the standard bar can grow)
- BottomNavigationSelectionTest (JVM): selection mapping logic
- BottomNavigationLayoutTest (androidTest): per-mode bar height assertions

* docs(navigation): warn that new Settings sub-pages must be added to settingsDestinations

Addresses agy review (PR #643): documents the fragility of the hardcoded settingsDestinations set so future Settings drill-down screens don't silently drop the bottom-nav highlight. The sealed-class/marker-interface refactor was declined as scope creep (issue #637 explicitly scopes Settings-only; keys are flat data objects).

* fix: language selector

---------

Co-authored-by: M57 <Hy4ri@users.noreply.github.com>

app/src/androidTest/java/com/m57/hermescontrol/BottomNavigationLayoutTest.kt

@@ -0,0 +1,60 @@
+package com.m57.hermescontrol
+
+import androidx.compose.foundation.layout.Box
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.testTag
+import androidx.compose.ui.test.assertHeightIsAtLeast
+import androidx.compose.ui.test.assertHeightIsEqualTo
+import androidx.compose.ui.test.junit4.createComposeRule
+import androidx.compose.ui.test.onNodeWithTag
+import androidx.compose.ui.unit.dp
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import androidx.test.filters.MediumTest
+import com.m57.hermescontrol.theme.BottomNavDisplayMode
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+
+/**
+ * Instrumented tests for [Modifier.bottomNavigationHeight].
+ *
+ * Each compact bottom-nav display mode maps to a specific bar height:
+ *  - [BottomNavDisplayMode.ICON_ONLY]      -> 56.dp (fixed)
+ *  - [BottomNavDisplayMode.TEXT_ONLY]      -> 44.dp (fixed)
+ *  - [BottomNavDisplayMode.ICON_AND_TEXT]  -> min 80.dp (can grow)
+ *
+ * We apply the modifier to a tagged [Box] and assert the resulting height on
+ * a real Compose host (this requires the instrumentation test runner, hence
+ * androidTest rather than the Robolectric-free JVM test source set).
+ */
+@RunWith(AndroidJUnit4::class)
+@MediumTest
+class BottomNavigationLayoutTest {
+    @get:Rule
+    val composeTestRule = createComposeRule()
+
+    @Test
+    fun iconOnly_barHeightIs56dp() {
+        composeTestRule.setContent {
+            Box(Modifier.testTag("bar").bottomNavigationHeight(BottomNavDisplayMode.ICON_ONLY))
+        }
+        composeTestRule.onNodeWithTag("bar").assertHeightIsEqualTo(56.dp)
+    }
+
+    @Test
+    fun textOnly_barHeightIs44dp() {
+        composeTestRule.setContent {
+            Box(Modifier.testTag("bar").bottomNavigationHeight(BottomNavDisplayMode.TEXT_ONLY))
+        }
+        composeTestRule.onNodeWithTag("bar").assertHeightIsEqualTo(44.dp)
+    }
+
+    @Test
+    fun iconAndText_barHeightIsAtLeast80dp() {
+        composeTestRule.setContent {
+            Box(Modifier.testTag("bar").bottomNavigationHeight(BottomNavDisplayMode.ICON_AND_TEXT))
+        }
+        // heightIn(min = 80.dp) — assert the measured height meets the minimum.
+        composeTestRule.onNodeWithTag("bar").assertHeightIsAtLeast(80.dp)
+    }
+}