fix(ui): settings modal sizing regression + 17 more folds audit findings

Fix settings modal regression: Modal500 was wrapped in useModalStyle(560),
forcing maxWidth 560px and squishing the two-pane Settings layout (folds
size="500" is ~50rem). Restore desktop width to the folds recipe while
keeping mobile fullscreen.

N-series fixes:
- N13 ScheduledMessagesTray header: <Box as="button"> -> folds <Button>
- N28 composer char counter: drop undefined --tc-surface-low + opacity,
  use priority="300" and config.space token
- N31 collapsible "Read more" toggle: padded <Button> -> flush inline-button
  pattern matching (edited) link
- N41 UserPrivateNotes "Saving..." now shows a folds <Spinner>
- N43 Night Light slider: add accentColor; label opacity -> priority
- N44 mention-highlight Reset: bare <button> -> folds <Button> (drops
  undefined --border-interactive-normal); Boot button kept (TDS-only)
- N45 SelectTheme trigger variant -> Secondary to match SettingsSelect
- N49 RoomInsights StatTile emoji -> folds <Icon> (Photo/VideoCamera/
  Headphone/File)
- N54/N57 PiP overlay badges + fullscreen button: token discipline
  (config.radii/space, folds Text); dark scrim kept for video legibility
- N60 knock badge: match Pinned Messages pattern (no wrapper div, toRem
  insets, no hardcoded size overrides)
- N62 unverified-device banner: 3px left-accent -> standard border via
  color.Warning.ContainerLine; drop opacity hacks
- N65 Edit History: real "Load more" pagination (accumulate next_batch,
  de-dupe by id, re-sort by ts) replacing passive text
- N66 search date fields: raw <input type="date"> -> folds <Input>
- N67 SeasonalEffect z-index 9999 -> 9997 (below Night Light + modals)
- N73 Pending Requests header uses css.MembersGroupLabel
- N74 remove raw em-sized emoji <span> in RoomNavItem name
- N85/N86 RemindMeDialog: <Box role="dialog"> -> folds <Dialog>; preset
  MenuItems -> Buttons (fixes invalid menuitem-in-dialog ARIA)

Document deliberate WON'T FIX rationale for N9, N51, N61, N71, N75, N77.

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

src/app/features/settings/general/General.tsx

@@ -123,7 +123,7 @@ function SelectTheme({ disabled }: { disabled?: boolean }) {
     <>
       <Button
         size="300"
-        variant="Primary"
+        variant="Secondary"
         outlined
         fill="Soft"
         radii="300"
@@ -549,7 +549,7 @@ function Appearance() {
             gap="100"
             style={{ padding: `0 ${config.space.S400} ${config.space.S300}` }}
           >
-            <Text size="T200" style={{ opacity: 0.7 }}>
+            <Text size="T200" priority="300">
               Intensity: {nightLightOpacity}%
             </Text>
             <input
@@ -560,7 +560,7 @@ function Appearance() {
               onChange={(e: React.ChangeEvent<HTMLInputElement>) =>
                 setNightLightOpacity(parseInt(e.target.value, 10))
               }
-              style={{ width: '100%' }}
+              style={{ width: '100%', accentColor: color.Primary.Main }}
             />
           </Box>
         )}
@@ -655,21 +655,16 @@ function Appearance() {
                 }}
               />
               {mentionHighlightColor && (
-                <button
+                <Button
                   type="button"
                   onClick={() => setMentionHighlightColor('')}
-                  style={{
-                    background: 'none',
-                    border: '1px solid var(--border-interactive-normal)',
-                    borderRadius: '6px',
-                    padding: '2px 8px',
-                    cursor: 'pointer',
-                    color: 'inherit',
-                    fontSize: '12px',
-                  }}
+                  size="300"
+                  variant="Secondary"
+                  fill="Soft"
+                  radii="300"
                 >
-                  Reset
-                </button>
+                  <Text size="B300">Reset</Text>
+                </Button>
               )}
             </Box>
           }