fix(theme): remove every hardcoded Apple/Material colour left in the UI

Porting the palette was not enough: the Warm Cinema charter only reached the
widgets that read from AppColors. Nineteen screen and widget files still painted
Apple TV values inline, so the app kept showing blue — most visibly on the
selected navigation pill.

Swept out:
- 0xFF0A84FF (Apple blue) on the selected nav pill, category card icons and the
  "add playlist" button
- 0xFF4FC3F7 and 0xFF1565C0 in the player overlays
- Colors.blueAccent / Colors.blue in dialogs
- Apple greys 1C1C1E / 2C2C2E / 3A3A3C / 8E8E93 -> warm charcoals
- 128 Colors.white* -> the onSurfaceNN cream ladder (a pure white on a warm
  ground reads blue, which is the charter's whole point)
- Colors.red / green / amber / yellow / grey* -> error, success, ratingGold,
  outlineVariant
- pure black ink on light fills -> onPrimaryFixed, a warm near-black
- the white focus glow -> an ember glow

Deliberately left true black: the video surface backgrounds and the scrims over
posters and video, where a warm tint would clash with the picture.

Adds the onPrimaryFixed / primaryFixed / onSurface70 tokens the sweep needed.

Verified: no Material or Apple colour literal remains outside lib/core/theme;
flutter analyze reports no errors; 19/19 tests pass; release APK builds.

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

lib/core/utils/image_cache_config.dart

@@ -10,6 +10,7 @@ library;
 import 'package:cached_network_image/cached_network_image.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_cache_manager/flutter_cache_manager.dart';
+import 'package:xtremobile/core/theme/app_colors.dart';
 
 /// Standard cache manager with 200MB size limit
 class AppCacheManager {
@@ -103,7 +104,7 @@ class ImageCacheConfig {
         width: width,
         height: height,
         decoration: BoxDecoration(
-          color: const Color(0xFF2C2C2E),
+          color: AppColors.surfaceContainer,
           borderRadius: BorderRadius.circular(8),
         ),
       ),
@@ -111,10 +112,10 @@ class ImageCacheConfig {
         width: width,
         height: height,
         decoration: BoxDecoration(
-          color: const Color(0xFF3A3A3C),
+          color: AppColors.surfaceContainerHigh,
           borderRadius: BorderRadius.circular(8),
         ),
-        child: const Icon(Icons.image_not_supported, color: Color(0xFF8E8E93)),
+        child: const Icon(Icons.image_not_supported, color: AppColors.textTertiary),
       ),
     );
   }