feat(theme): complete redesign to Cyber-Cinematic Glass (Stitch)

Replace the legacy Apple TV-style purple/cyan theme with the full
Google Stitch Cyber-Cinematic Glass design system across the
entire app (desktop + mobile).

- New Material 3 dark ColorScheme: background #121317, primary
  #adc6ff, primaryContainer #4b8eff, surface containers, etc.
- Typography: Space Grotesk (headlines) + Inter (body/labels)
- 3-level glassmorphism via GlassContainer: base, glass, floating
- Primary gradient: #007AFF → #00C6FF with blue glow effects
- Removed old compatibility aliases (focusColor, border, textPrimary,
  textSecondary); all code now uses semantic Stitch tokens
- Systematically replaced all Colors.white/black/red/grey and
  GoogleFonts.roboto/outfit with Stitch equivalents
- All 36 lib/ files updated, zero compilation errors

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

lib/mobile/widgets/mobile_scaffold.dart

@@ -2,6 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:google_fonts/google_fonts.dart';
 import 'dart:ui';
+import '../../../core/theme/app_colors.dart';
 
 class MobileScaffold extends ConsumerWidget {
   final Widget child;
@@ -19,7 +20,7 @@ class MobileScaffold extends ConsumerWidget {
   Widget build(BuildContext context, WidgetRef ref) {
     return Scaffold(
       extendBody: true,
-      backgroundColor: Colors.black, // Base color
+      backgroundColor: AppColors.background,
       body: Stack(
         fit: StackFit.expand,
         children: [
@@ -30,8 +31,8 @@ class MobileScaffold extends ConsumerWidget {
                 center: Alignment.center,
                 radius: 1.5,
                 colors: [
-                  Color(0xFF1C1C1E),
-                  Color(0xFF000000),
+                  AppColors.surfaceContainerLow,
+                  AppColors.background,
                 ],
               ),
             ),
@@ -46,10 +47,10 @@ class MobileScaffold extends ConsumerWidget {
           filter: ImageFilter.blur(sigmaX: 20, sigmaY: 20),
           child: Container(
             decoration: BoxDecoration(
-              color: const Color(0xFF1C1C1E).withOpacity(0.85),
+              color: AppColors.surfaceContainerLow.withOpacity(0.85),
               border: Border(
                 top: BorderSide(
-                  color: Colors.white.withOpacity(0.1),
+                  color: AppColors.outlineVariant.withOpacity(0.5),
                   width: 0.5,
                 ),
               ),
@@ -60,8 +61,8 @@ class MobileScaffold extends ConsumerWidget {
               backgroundColor: Colors.transparent,
               type: BottomNavigationBarType.fixed,
               elevation: 0,
-              selectedItemColor: Colors.white,
-              unselectedItemColor: Colors.white38,
+              selectedItemColor: AppColors.onSurface,
+              unselectedItemColor: AppColors.onSurfaceVariant,
               selectedLabelStyle:
                   GoogleFonts.inter(fontWeight: FontWeight.w600, fontSize: 11),
               unselectedLabelStyle: