feat: add gif slash command - #1573

> **Preview the next release on [dev.sable.moe](https://dev.sable.moe)**

> [!IMPORTANT]
> Merging this PR will create a new release.

## Features

* Add the `forum` room type with a dedicated forum view that presents
threads as topics. by @smokku in #980
* New composer commands: `/gif` opens the GIF picker and `/rainbowme`
sends rainbow-formatted action messages (#1109). by @eleboucher in #1573
* Add selectable app icons on Android and iOS. by @eleboucher in #1594
* Add MSC4466 profile sync controls for supported homeservers. by @7w1
in #1117
* Add experimental new calls using LiveKit on web, desktop, and
supported mobile devices, enabled by a single setting with Element Call
as the fallback. by @eleboucher in #1575
* Add toggleable, reorderable composer trigger buttons (emoji, gif,
sticker) with a drag-and-drop settings list. by @eleboucher in #1261
* Settings improvements: search the settings sidebar and customize
keyboard shortcuts (#1121). by @eleboucher in #1660
* Add an accessibility settings tab with color correction filters. by
@j0lol in #1664
* Persona improvements: pick a persona directly in the editor, an
account-wide persona toggle, latching shorthands, persona name colors,
and a redesigned persona settings menu (#1223, #1264, #1368, #1369,
#1435, #1462). by @j0lol in #1171
* Style tables in formatted messages. by @Steffo99 in #1580
* New bottom sheets across the app: attach files and pick emoji from
sheets in the composer, plus a room details sheet on small screens
(#1173, #1433). by @eleboucher in #1234
* Update the device display name after login to reflect the current
client and build flavor. by @hazre in #1458
* Replaced the connection status top bar with a small styled popup and
added a variant that shows sliding sync initial progress. by @7w1 in
#1200
* Add per-message profiles (MSC4461): a different name and avatar in
each room, with PluralKit import, shorthands, backup and restore,
editing sent messages, and profile info on user profiles (#1352, #1479,
#1586, #1611, #1651, #1701). by @j0lol in #1589
* The notifications inbox is now built from push rules evaluated on this
device instead of the server's `/notifications` endpoint, so mentions in
encrypted rooms are detected correctly. by @eleboucher in #1372
* Add beta desktop and mobile builds with a greatly improved mobile
experience, UnifiedPush support and more reliable notifications, better
desktop shortcuts, updates and window controls, and improved native
media handling and sharing. by @eleboucher in #1103

## Fixes

* Publish an `obtainium.json` app config with every release so Android
builds can be installed and auto-updated through Obtainium. by
@eleboucher in #1616
* Performance: faster startup and warm syncs by caching room metadata,
profile data, and device verification, plus lower memory use by pruning
inactive room history (#1127, #1184, #1305, #1466). by @7w1 in #1118
* Login and account fixes: full-URL homeservers no longer land on an
empty room, a retry button when discovery fails, OAuth device
verification no longer hangs, identity reset completes, key backup
restores on verified devices, and account switch or logout from the
offline screen (#1115, #1270, #1348, #1379, #1380). by @eleboucher in
#1582
* Media fixes: encrypted images and GIFs render again, playback works on
Firefox, better loading on slow connections, decrypted media is freed
from memory, gzipped Lottie support, stickers send reliably, and
notification sounds no longer play as media (#1104, #1296, #1331, #1332,
#1334, #1353, #1381). by @eleboucher in #1271
* Fix link previews leaving empty space in a message until it is
reloaded by @eleboucher in #1827
* Message formatting fixes: checklists no longer render as raw HTML,
spoilers work with proxy tags, maps with malformed coordinates no longer
crash the app, and membership reasons are wrapped in parentheses (#1248,
#1307, #1470). by @eleboucher in #1354
* Fix context menus closing instead of opening, keep the room options
sheet open, and let sidebar, space, and image viewer menus open on
long-press as well as right-click (#1336, #1358). by @eleboucher in
#1431
* Assorted fixes: popups on start appear one at a time, room leave
updates immediately, accepted invites stop reappearing, synced CSS
tweaks are restored, the scheduled-messages chip shows again, faster
recovery from network switches, plus small visual and formatting fixes
(#1114, #1120, #1146, #1200, #1220, #1284, #1514, #1656). by @eleboucher
in #1399
* Profile fixes: hero colours and full scrolling restored on profile
sheets, local time respects the 24-hour setting, devices stay sorted
when last-active times are missing, and no crash in room cosmetics
before members load (#1298, #1579, #1793). by @eleboucher in #1503
* Fix sliding sync issues: missing or stale display names, bridged
avatars, blank space icons, sticker and emote packs, subspaces, call
updates, and incomplete member lists (#1111, #1112, #1119, #1173, #1530,
#1554). by @7w1 in #1170
* Notification and unread fixes: rooms no longer stay unread after a
thread reply or restart, the inbox shows real message previews, the page
title shows the mention count, and tapping a notification navigates
correctly (#1245, #1390). by @eleboucher in #1816
* Timeline fixes: reliably follow new messages, stop loading a room's
whole history on open, unstuck pagination, restored polls, and fixed
thread rendering, reactions, and replies (#1113, #1358, #1363, #1367,
#1373, #1425). by @eleboucher in #1105
* Fix voice recordings continuing after cancel or rapid taps, and stop
the microphone when a recording is interrupted before the permission
prompt resolves (#1428). by @eleboucher in #1252
* Add option to always keep the last line of the text editor "inline"
with the UI buttons. by @lunar-seal in #1218
* Mobile polish: smoother swipe navigation and drawer, steady keyboard
while editing, better touch feedback, chat input and account panel,
swipe-to-edit on messages, and fixed swiping in attachments (#1103,
#1130, #1131, #1144, #1173, #1267, #1303, #1382, #1754). by @eleboucher
in #1166