feat(P3-6): configurable composer toolbar buttons

Each button (Format, Emoji, Sticker, GIF, Location, Poll, Voice,
Schedule) can be individually hidden in Settings → Editor.
All default to on, stored in composerToolbarButtons object.
getSettings deep-merges the nested object so new buttons default
to true for existing users with saved settings.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/state/settings.ts

@@ -38,6 +38,28 @@ export enum MessageLayout {
   Bubble = 2,
 }
 
+export interface ComposerToolbarSettings {
+  showFormat: boolean;
+  showEmoji: boolean;
+  showSticker: boolean;
+  showGif: boolean;
+  showLocation: boolean;
+  showPoll: boolean;
+  showVoice: boolean;
+  showSchedule: boolean;
+}
+
+export const DEFAULT_COMPOSER_TOOLBAR: ComposerToolbarSettings = {
+  showFormat: true,
+  showEmoji: true,
+  showSticker: true,
+  showGif: true,
+  showLocation: true,
+  showPoll: true,
+  showVoice: true,
+  showSchedule: true,
+};
+
 export interface Settings {
   themeId?: string;
   useSystemTheme: boolean;
@@ -101,6 +123,8 @@ export interface Settings {
   warnOnUnverifiedDevices: boolean;
 
   pauseAnimations: boolean;
+
+  composerToolbarButtons: ComposerToolbarSettings;
 }
 
 const defaultSettings: Settings = {
@@ -166,13 +190,23 @@ const defaultSettings: Settings = {
   warnOnUnverifiedDevices: false,
 
   pauseAnimations: false,
+
+  composerToolbarButtons: DEFAULT_COMPOSER_TOOLBAR,
 };
 
 export const getSettings = (): Settings => {
   try {
     const settings = localStorage.getItem(STORAGE_KEY);
     if (settings === null) return defaultSettings;
-    return { ...defaultSettings, ...(JSON.parse(settings) as Settings) };
+    const saved = JSON.parse(settings) as Partial<Settings>;
+    return {
+      ...defaultSettings,
+      ...saved,
+      composerToolbarButtons: {
+        ...DEFAULT_COMPOSER_TOOLBAR,
+        ...(saved.composerToolbarButtons ?? {}),
+      },
+    };
   } catch {
     localStorage.removeItem(STORAGE_KEY);
     return defaultSettings;