Android chat UX: video viewer, emoji/gif/sticker picker, day separators

android/CHANGELOG.md

@@ -943,3 +943,17 @@
 - Notification delivery polish (foundation):
   - foreground notification body now respects preview setting and falls back to media-type labels when previews are disabled.
 - Verified with successful `:app:compileDebugKotlin` and `:app:assembleDebug`.
+
+### Step 130 - Chat UX pack: video viewer, emoji/GIF/sticker picker, day separators
+- Added chat timeline day separators with Telegram-like chips:
+  - `Сегодня`, `Вчера`, or localized date labels.
+- Added fullscreen video viewer:
+  - video attachments now open in a fullscreen overlay with close action.
+- Added composer media picker sheet:
+  - tabs: `Эмодзи`, `GIF`, `Стикеры`,
+  - emoji insertion at cursor,
+  - remote GIF/sticker selection with download+send flow.
+- Extended media type mapping in message send pipeline:
+  - GIFs now sent as `gif`,
+  - sticker-like payloads sent as `sticker` (filename/mime detection).
+- Added missing fallback resource theme declarations (`themes.xml`) to stabilize clean debug assembly on local builds.