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/widgets/digital_clock.dart

@@ -2,6 +2,7 @@ import 'dart:async';
 import 'package:flutter/material.dart';
 import 'package:google_fonts/google_fonts.dart';
 import 'package:intl/intl.dart';
+import 'package:xtremobile/core/theme/app_colors.dart';
 
 class DigitalClock extends StatefulWidget {
   const DigitalClock({super.key});
@@ -31,16 +32,16 @@ class _DigitalClockState extends State<DigitalClock> {
         return Container(
           padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 8),
           decoration: BoxDecoration(
-            color: Colors.white.withOpacity(0.1),
+            color: AppColors.onSurface.withOpacity(0.1),
             borderRadius: BorderRadius.circular(20),
-            border: Border.all(color: Colors.white.withOpacity(0.05)),
+            border: Border.all(color: AppColors.onSurface.withOpacity(0.05)),
           ),
           child: Text(
             timeString,
             style: GoogleFonts.inter(
               fontWeight: FontWeight.w600,
               fontSize: 16,
-              color: Colors.white,
+              color: AppColors.onSurface,
             ),
           ),
         );