feat: add album preview sheet before sending

- open a media preview sheet for picked photos and videos before upload

- support reordering, removing items, and editing the shared caption in the sheet

- send the confirmed batch through the existing album flow as one message with attachments

android/app/src/main/res/values/strings.xml

@@ -351,4 +351,8 @@
     <string name="account_error_invalid_credentials">Invalid credentials.</string>
     <string name="account_error_unauthorized">Unauthorized.</string>
     <string name="chat_audio_strip_video_note">Video note</string>
+    <string name="chat_media_preview_title">%1$d selected</string>
+    <string name="chat_media_preview_caption_hint">Add a caption</string>
+    <string name="chat_media_preview_move_left">Move left</string>
+    <string name="chat_media_preview_move_right">Move right</string>
 </resources>