feat(design): Warm Cinema redesign + fast-start players

Full visual overhaul from Cyber-Cinematic Glass to "Warm Cinema":
warm charcoal (#0B0908), cream (#F3E9DF), ember (#D9541F).
Fraunces (editorial serif) for display, Karla for body/UI.

Design
- app_colors: new palette, all existing token names preserved,
  plus posterScrim/heroScrim gradients and lift()/emberFocus() shadows
- app_theme: new type scale, tighter radii, 20+ component themes
- mobile_theme aligned on the same tokens
- glass_container: opaque layered surfaces replace glassmorphism;
  adds GlassCard (hover + remote-focus states) and CinemaBackdrop
- players and boot splash restyled (film-leader motif, no web fonts)

Performance
- remove every BackdropFilter (33 call sites): backdrop blur forced a
  full framebuffer read per frame per card, the main scroll jank source
- bundle Fraunces/Karla as assets: google_fonts no longer fetches from
  fonts.gstatic.com at startup
- drop the blocking hls.js CDN script from index.html; no Dart code
  ever used it, only the player iframes need it
- self-host hls.js/mpegts.js and load them on demand, so ~213 KB of
  mpegts is never downloaded for HLS streams
- bound image decode size on 10 sites: a 40-poster grid drops from
  ~240 MB to a few tens of MB of GPU memory

Players (new shared engine: web/xf-player-core.js)
- event-driven start instead of a 200 ms buffer poll plus a 1.5 s wait
- initialLiveManifestSize 3 -> 1, liveSyncDurationCount 10 -> 2,
  startFragPrefetch on, testBandwidth off
- MPEG-TS initial stash 512 KB -> 64 KB
- adaptive escalation fast -> balanced -> safe on repeated stalls
  (60 s rolling window), applied live for HLS so there is no visible cut

Pre-existing build breakage fixed along the way
- undefined AppColors.shimmer, AppTheme.durationXs and spacing8/12/16/32
- broken relative imports in channel_card and quality_selector_widget
- missing GlassCard widget and hasBorder/showShadow parameters

Also resolves a leftover unmerged .claude/settings.local.json by
keeping the remote version.

Still broken (pre-existing, dead code, not reachable from main.dart):
recommendations_provider.dart and continue_watching_widget.dart import
a models/playlist.dart that no longer exists.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

lib/features/admin/screens/admin_panel.dart

@@ -152,7 +152,7 @@ class _AdminContentState extends ConsumerState<AdminContent>
                 const SizedBox(width: 8),
                 Text(
                   label,
-                  style: GoogleFonts.inter(
+                  style: GoogleFonts.karla(
                     fontWeight: FontWeight.w600,
                     fontSize: 14,
                     color: isSelected ? AppColors.textPrimary : AppColors.textSecondary,
@@ -265,7 +265,7 @@ class _PlaylistsTab extends ConsumerWidget {
                                 style: Theme.of(context)
                                     .textTheme
                                     .titleMedium
-                                    ?.copyWith(color: Colors.white),
+                                    ?.copyWith(color: AppColors.onSurface),
                               ),
                               const SizedBox(height: 4),
                               Text(
@@ -273,7 +273,7 @@ class _PlaylistsTab extends ConsumerWidget {
                                 style: Theme.of(context)
                                     .textTheme
                                     .bodyMedium
-                                    ?.copyWith(color: Colors.white60),
+                                    ?.copyWith(color: AppColors.onSurface54),
                               ),
                             ],
                           ),
@@ -282,7 +282,7 @@ class _PlaylistsTab extends ConsumerWidget {
                           children: [
                             IconButton(
                               icon: const Icon(Icons.edit_outlined, size: 20),
-                              color: Colors.white70,
+                              color: AppColors.onSurfaceVariant,
                               onPressed: () =>
                                   _showPlaylistDialog(context, ref, playlist),
                               tooltip: 'Edit',
@@ -544,7 +544,7 @@ class _UsersTab extends ConsumerWidget {
                                     style: Theme.of(context)
                                         .textTheme
                                         .titleMedium
-                                        ?.copyWith(color: Colors.white),
+                                        ?.copyWith(color: AppColors.onSurface),
                                   ),
                                   if (user.isAdmin) ...[
                                     const SizedBox(width: 8),
@@ -576,7 +576,7 @@ class _UsersTab extends ConsumerWidget {
                                 style: Theme.of(context)
                                     .textTheme
                                     .bodyMedium
-                                    ?.copyWith(color: Colors.white60),
+                                    ?.copyWith(color: AppColors.onSurface54),
                               ),
                             ],
                           ),
@@ -584,7 +584,7 @@ class _UsersTab extends ConsumerWidget {
                         PopupMenuButton<String>(
                           icon: const Icon(
                             Icons.more_vert,
-                            color: Colors.white70,
+                            color: AppColors.onSurfaceVariant,
                           ),
                           color: AppColors.surface,
                           shape: RoundedRectangleBorder(