fix(mobile): 44px touch targets for primary call/thread/mod controls (P1)

Deep-audit follow-up. New shared MobileTouchTarget class (@media <=750px ->
minWidth/minHeight 44px) applied via className to the primary interactive
controls folds renders below 44px:
- in-call control bar (7 buttons) + persistent call-status bar (4 buttons)
- thread "N replies" chip
- knock Approve/Deny buttons
- server-ACL entry remove button

folds size variants set only padding (no width/height/min-*), so the class
raises the hit-area floor to 44px with the icon/label staying centered at its
normal size; desktop is untouched (@media-gated). Verified by two review passes
(no distortion, no layout overflow, counts exact).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/features/room/thread/ThreadSummary.tsx

@@ -1,6 +1,7 @@
 import React from 'react';
 import { Badge, Box, Chip, Icon, Icons, Text, config } from 'folds';
 import { MatrixEvent, Room } from 'matrix-js-sdk';
+import { MobileTouchTarget } from '../../../styles/mobile.css';
 import { useThreadSummary } from '../../../hooks/useThreadSummary';
 import { useSetting } from '../../../state/hooks/settings';
 import { settingsAtom } from '../../../state/settings';
@@ -31,6 +32,7 @@ export function ThreadSummary({ rootEvent, room, onOpen }: ThreadSummaryProps) {
       <Chip
         variant="SurfaceVariant"
         radii="300"
+        className={MobileTouchTarget}
         before={<Icon size="50" src={Icons.Thread} />}
         after={
           unread > 0 ? <Badge variant="Success" fill="Solid" radii="Pill" size="200" /> : undefined