feat(design): Warm Cinema theme + event-driven adaptive players

Replaces the Projector Noir palette with "Warm Cinema" and rebuilds the
web players around a shared, event-driven engine.

Design
- app_colors: warm charcoal (#0B0908), cream (#F3E9DF), ember (#D9541F);
  adds posterScrim/heroScrim gradients, lift()/emberFocus() shadows,
  const cream-alpha tokens replacing Colors.whiteNN, and primaryFill,
  a deeper ember reserved for text-bearing fills so white labels clear
  the 4.5:1 AA threshold that #D9541F alone does not
- app_theme / mobile_theme: Fraunces (display serif) + Karla (body),
  tighter radii, 20+ component themes
- glass_container: opaque layered surfaces replace the blurred glass
- themed_loading_screen restyled; players and boot splash follow

Performance
- drop every BackdropFilter: backdrop blur forced a full framebuffer
  read per frame per card, the main source of scroll jank
- bundle Fraunces/Karla as assets so google_fonts stops fetching from
  fonts.gstatic.com at startup
- bound image decode size on 12 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)
- start on media events instead of polling the buffer every 100-200 ms
- hls.js/mpegts.js loaded on demand, so ~213 KB of mpegts is never
  fetched for HLS streams
- liveSyncDurationCount 10 -> 2, startFragPrefetch on, testBandwidth
  off, MPEG-TS initial stash 512 KB -> 64 KB
- adaptive escalation fast -> balanced -> safe after repeated stalls in
  a 60 s window, applied live for HLS so there is no visible cut

Preserved from the recent streaming work on main: server-side quality
selection, stable player viewId, the turbo direct MPEG-TS path, vendored
library cache headers and the CI/Docker changes. Only the theme layer and
the player front-end were replaced; GlassCard stays in ui_components.

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

lib/mobile/features/auth/screens/mobile_login_screen.dart

@@ -124,7 +124,7 @@ class _MobileLoginScreenState extends ConsumerState<MobileLoginScreen> {
                       const SizedBox(height: 24),
                       Text(
                         'XtremFlow',
-                        style: GoogleFonts.syne(
+                        style: GoogleFonts.fraunces(
                           fontSize: 32,
                           fontWeight: FontWeight.w700,
                           color: AppColors.onSurface,
@@ -133,7 +133,7 @@ class _MobileLoginScreenState extends ConsumerState<MobileLoginScreen> {
                       ),
                        Text(
                         'Mobile Edition',
-                        style: GoogleFonts.instrumentSans(
+                        style: GoogleFonts.karla(
                           fontSize: 14,
                           color: AppColors.onSurfaceVariant,
                           letterSpacing: 0.5,
@@ -173,7 +173,7 @@ class _MobileLoginScreenState extends ConsumerState<MobileLoginScreen> {
                                 ),
                                 child: Text(
                                   authState.errorMessage!,
-                                  style: GoogleFonts.instrumentSans(color: AppColors.error, fontSize: 13),
+                                  style: GoogleFonts.karla(color: AppColors.error, fontSize: 13),
                                   textAlign: TextAlign.center,
                                 ),
                               ),
@@ -199,7 +199,7 @@ class _MobileLoginScreenState extends ConsumerState<MobileLoginScreen> {
                                 onPressed: authState.isLoading ? null : _handleLogin,
                                 style: FilledButton.styleFrom(
                                   backgroundColor: Colors.transparent,
-                                  foregroundColor: Colors.white,
+                                  foregroundColor: AppColors.onSurface,
                                   shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(12)),
                                   elevation: 0,
                                 ).copyWith(
@@ -209,11 +209,11 @@ class _MobileLoginScreenState extends ConsumerState<MobileLoginScreen> {
                                     ? const SizedBox(
                                         width: 24,
                                         height: 24,
-                                        child: CircularProgressIndicator(strokeWidth: 2, color: Colors.white),
+                                        child: CircularProgressIndicator(strokeWidth: 2, color: AppColors.onSurface),
                                       )
                                     : Text(
                                         'Sign In',
-                                        style: GoogleFonts.instrumentSans(fontWeight: FontWeight.w600, fontSize: 16, color: Colors.white),
+                                        style: GoogleFonts.karla(fontWeight: FontWeight.w600, fontSize: 16, color: AppColors.onSurface),
                                       ),
                               ),
                             ),
@@ -243,10 +243,10 @@ class _MobileLoginScreenState extends ConsumerState<MobileLoginScreen> {
     return TextFormField(
       controller: controller,
       obscureText: obscureText,
-      style: GoogleFonts.instrumentSans(color: AppColors.onSurface),
+      style: GoogleFonts.karla(color: AppColors.onSurface),
       decoration: InputDecoration(
         labelText: label,
-        labelStyle: GoogleFonts.instrumentSans(color: AppColors.onSurfaceVariant),
+        labelStyle: GoogleFonts.karla(color: AppColors.onSurfaceVariant),
         prefixIcon: Icon(icon, color: AppColors.onSurfaceVariant),
         suffixIcon: isPassword
           ? IconButton(