chore: prepare release 1.21.0

[sable-actions]

Preview the next release on dev.sable.moe

Important

Merging this PR will create a new release.

Features

• Add MSC4466 profile sync controls for supported homeservers. (#1117 by @7w1)
• Add toggleable, reorderable composer trigger buttons (emoji, gif, sticker) with a drag-and-drop settings list. (#1261 by @eleboucher)
• Add Persona picker in Editor (#1171)
• Attach files and media from a bottom sheet on the message input. (#1234 by @eleboucher)
• Clean up the design of Persona settings (#1223)
• Add desktop keyboard shortcuts to open settings, toggle window visibility, and quit. (#1153 by @7w1, @eleboucher)
• Improve desktop window layout with seamless macOS titlebars and custom Linux controls. (#1153 by @7w1, @eleboucher)
• Replaced the connection status top bar with a small styled popup and added a variant that shows sliding sync initial progress. (#1200 by @7w1)
• Improve mobile UX with native back button support, haptics, and iOS keyboard handling. (#1153 by @7w1, @eleboucher)
• Add native push notifications with reply actions, content preview, and configurable gateway (#1238 by @eleboucher)
• Share content via native system share menu or copy links on desktop. (#1148 by @eleboucher)
• Share text, media, and files into Sable directly from other mobile apps. (#1159 by @7w1, @eleboucher, @mortebrume)
• Add beta builds for desktop and mobile. (#1103 by @7w1, @eleboucher, @hazre, @mortebrume, @nikiwastaken, @TastelessVoid)

Fixes

• Added a modal for viewing room details on mobile. (#1173 by @7w1)
• Add account switching and logout actions to the offline screen. (#1115 by @7w1)
• Improve Android media uploads with streaming progress tracking and automatic temp file cleanup. (#1154 by @eleboucher)
• Cache room metadata for faster sliding sync warm starts. (#1118 by @7w1)
• Dismiss overlays on Android system back instead of navigating away. (#1249 by @7w1, @eleboucher)
• Fix media loading stalling on Android when browsing history. (#1129 by @eleboucher)
• Keep message input focused after selecting autocomplete suggestions on mobile. (#1103 by @7w1, @eleboucher, @hazre, @mortebrume, @nikiwastaken, @TastelessVoid)
• Made popups on start appear sequentially instead of bombarding all at once. (#1200 by @7w1)
• Fix missing profile pictures for bridged users in timeline when using sliding sync. (#1112 by @7w1, @eleboucher)
• Fix Maps that contain incorrect numbers for lat/lon crashing sable (#1248 by @nushea)
• Fix room leaving state not updating immediately in UI. (#1146 by @7w1)
• Fixed needs to double tap a room on android (#1175 by @eleboucher)
• Smooth out animation when tapping 'following the conversation'. (#1173 by @7w1)
• Fix keyboard flickering when editing messages on mobile. (#1130 by @eleboucher)
• Improve mobile touch feedback and prevent accidental presses. (#1173 by @7w1)
• Smoother mobile navigation and faster room opening. (#1144 by @eleboucher)
• Changed the web page title to show the mention count instead of the total unread message count. (#1245 by @eleboucher)
• Fix missing user display names under sliding sync across search, notifications, threads, and replies. (#1170 by @7w1)
• Fix display names in read receipts and event details when using sliding sync with member drawer closed. (#1111 by @7w1)
• Fix sliding sync not subscribing to call updates. (#1173 by @7w1)
• Fix subspaces with emote packs listed as separate spaces under sliding sync. (#1119 by @mortebrume)
• Fix space icons staying blank on first open with sliding sync. (#1112 by @7w1, @eleboucher)
• Fix loading space-hosted sticker and emote packs when using sliding sync. (#1112 by @7w1, @eleboucher)
• Restore locally imported CSS tweaks when syncing settings between devices. (#1220 by @eleboucher)
• Fix timeline auto-scrolling to new messages when pinned to the bottom. (#1105 by @eleboucher)
• Prevent typing indicator from obscuring messages and stabilize timeline scroll snapping. (#1113 by @eleboucher)
• Various visual tweaks (#1114 by @nushea)
• Fix voice recording continuing indefinitely when the record button is rapidly tapped on Android. (#1252 by @7w1, @eleboucher)
• Fix overlapping Bookmarks and Bold Text shortcut (#1120 by @cyrneko)
• Fix media 401 errors, improve slow-internet media loading, and add native streaming decryption for encrypted media in Tauri. (#1246 by @eleboucher)
• Allow using native window chrome instead of the custom title bar. (#1188 by @eleboucher)
• Improve app startup speed and eliminate initial launch screen flickering. (#1127 by @7w1, @eleboucher)
• Polish the account panel and settings layout on mobile. (#1131 by @eleboucher)
• Polish the mobile chat input with adaptive send and recording controls, easier photo attachment, and more reliable Android uploads. (#1166 by @7w1, @eleboucher)
• Improve message rendering consistency across views. (#1170 by @7w1)
• Add swipe-to-edit gesture on mobile messages. (#1267 by @7w1)
• Various performance improvements. (#1184 by @7w1)
• Made update popups use in-app modals instead of calling os native dialogs. (#1200 by @7w1)
• Updated OIDC implementation with new matrix-js-sdk version. (#1077 by @7w1, @eleboucher)