fix(ui): avatar-decoration reliability, Saved Messages + Media Gallery redesign

Avatar decorations: useAvatarDecoration cached ALL profile-field fetch
failures as "no decoration" permanently for the session. The member list
and timeline mount many avatars at once, so one rate-limited (429) burst
would wipe everyone's decoration until a full reload. Now only a genuine
404 (field unset) is cached; transient errors retry on the next mount.

Saved Messages panel — full redesign to match the canonical MembersDrawer:
- co-located BookmarksPanel.css.ts: toRem(266) + max-width:750px full-screen
  media query, replacing the old position:absolute/zIndex:100 mobile "modal"
  that had no backdrop or escape
- variant="Background" header; room avatars on each item (was a generic hash)
- priority tokens replace all raw opacity hacks; 3px borderLeft accent removed
- Escape-to-close; multi-line preview is now a proper folds Button (N38)

Media Gallery (N12): moved fixed positioning + width into MediaGallery.css.ts
using toRem(320) + a full-screen media query; border/header use config tokens;
added Escape-to-close on the panel (previously only the lightbox handled it).

Presence (SettingsTab / useUserPresence):
- N16: wrap presence-dot trigger in TooltipProvider; replace undefined
  --bg-surface with color.Background.Container
- N17: add escapeDeactivates + isKeyForward/isKeyBackward to the FocusTrap
- N19: align reader labels (usePresenceLabel) to the setter vocabulary
  (Online/Idle/Offline) so a chosen status matches the tooltip others see

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

src/app/features/room/MediaGallery.css.ts

@@ -0,0 +1,31 @@
+import { style } from '@vanilla-extract/css';
+import { color, config, toRem } from 'folds';
+
+// Right-side drawer that floats over the room view. 320px is wider than the
+// 266px member/bookmark drawers because it hosts a media grid; on narrow
+// viewports it expands to fill the screen, matching the app's other drawers.
+export const MediaGalleryDrawer = style({
+  position: 'fixed',
+  top: 0,
+  right: 0,
+  bottom: 0,
+  width: toRem(320),
+  zIndex: 500,
+  overflow: 'hidden',
+  borderLeftWidth: config.borderWidth.B300,
+  borderLeftStyle: 'solid',
+  borderLeftColor: color.Surface.ContainerLine,
+  '@media': {
+    '(max-width: 750px)': {
+      width: '100%',
+      borderLeftWidth: 0,
+    },
+  },
+});
+
+export const MediaGalleryHeader = style({
+  flexShrink: 0,
+  paddingRight: config.space.S200,
+  paddingLeft: config.space.S300,
+  borderBottomWidth: config.borderWidth.B300,
+});