feat(settings): in-app chat font size setting (#1004) (#1005)

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/main/java/com/m57/hermescontrol/data/config/ServerStoreState.kt

@@ -21,6 +21,7 @@ data class ServerStoreState(
     val wsAuthParam: String = "token",
     val typingEffectEnabled: Boolean = true,
     val typingEffectDelayMs: Int = 30,
+    val chatFontScale: Float = 1.0f,
     // App display language. "system" = follow device locale; otherwise a BCP-47
     // language code such as "en" or "ko". Applied via ContextWrapper in MainActivity.
     val appLanguage: String = "system",

app/src/main/java/com/m57/hermescontrol/data/local/AuthManager.kt

@@ -74,6 +74,9 @@ object AuthManager {
     private val _themePresetFlow = MutableStateFlow<ThemePreset>(ThemePreset.DEFAULT)
     val themePresetFlow: StateFlow<ThemePreset> = _themePresetFlow.asStateFlow()
 
+    private val _chatFontScaleFlow = MutableStateFlow<Float>(1.0f)
+    val chatFontScaleFlow: StateFlow<Float> = _chatFontScaleFlow.asStateFlow()
+
     private val _tokenFlow = MutableStateFlow<String?>(null)
     val tokenFlow: StateFlow<String?> = _tokenFlow.asStateFlow()
 
@@ -180,6 +183,7 @@ object AuthManager {
                     _themePreferenceFlow.value = state.themePreference
                     _useDynamicColorsFlow.value = state.useDynamicColors
                     _themePresetFlow.value = state.themePreset
+                    _chatFontScaleFlow.value = state.chatFontScale
                     // B7 (Jul 08 2026, kanban t_470): keep cookie scope aligned with active profile.
                     appScope?.launch { syncCookieStoreForProfile(state.selectedProfileId) }
                 }
@@ -640,6 +644,15 @@ object AuthManager {
         serverStore.update { it.copy(typingEffectDelayMs = delayMs) }
     }
 
+    // ── Chat Font Scale (issue #1004) ───────────────────────────────────
+
+    fun getChatFontScale(): Float = serverStore.getLatestState().chatFontScale
+
+    fun setChatFontScale(scale: Float) {
+        serverStore.update { it.copy(chatFontScale = scale) }
+        _chatFontScaleFlow.value = scale
+    }
+
     // ── In-app update check (issue #867) ─────────────────────────────────
 
     /** App version the silent update check last completed for (null = never). */