feat(ads): add AdThemeStyle model for native ad theming

- Create UI-agnostic data model for ad theme properties
- Implement factory constructor to adapt Flutter ThemeData
- Define properties for background colors, text colors, font sizes, and corner radius
- Use Equatable for easy comparison and hashing

Author: fulleni

lib/ads/models/ad_theme_style.dart

@@ -0,0 +1,117 @@
+import 'package:equatable/equatable.dart';
+import 'package:flutter/material.dart';
+import 'package:ui_kit/ui_kit.dart';
+
+/// {@template ad_theme_style}
+/// A UI-agnostic data model representing the theme properties required for
+/// styling native advertisements.
+///
+/// This class decouples ad styling logic from Flutter's [ThemeData],
+/// allowing theme-related values to be passed to service layers without
+/// direct UI context dependencies.
+/// {@endtemplate}
+class AdThemeStyle extends Equatable {
+  /// {@macro ad_theme_style}
+  const AdThemeStyle({
+    required this.mainBackgroundColor,
+    required this.cornerRadius,
+    required this.callToActionTextColor,
+    required this.callToActionBackgroundColor,
+    required this.callToActionTextSize,
+    required this.primaryTextColor,
+    required this.primaryBackgroundColor,
+    required this.primaryTextSize,
+    required this.secondaryTextColor,
+    required this.secondaryBackgroundColor,
+    required this.secondaryTextSize,
+    required this.tertiaryTextColor,
+    required this.tertiaryBackgroundColor,
+    required this.tertiaryTextSize,
+  });
+
+  /// Factory constructor to create an [AdThemeStyle] from a Flutter [ThemeData].
+  ///
+  /// This method acts as an adapter, extracting the relevant styling properties
+  /// from the UI's theme and mapping them to the UI-agnostic [AdThemeStyle] model.
+  factory AdThemeStyle.fromTheme(ThemeData theme) {
+    final colorScheme = theme.colorScheme;
+    final textTheme = theme.textTheme;
+
+    return AdThemeStyle(
+      mainBackgroundColor: colorScheme.surface,
+      cornerRadius: AppSpacing.sm, 
+      callToActionTextColor: colorScheme.onPrimary,
+      callToActionBackgroundColor: colorScheme.primary,
+      callToActionTextSize: textTheme.labelLarge?.fontSize,
+      primaryTextColor: colorScheme.onSurface,
+      primaryBackgroundColor: colorScheme.surface,
+      primaryTextSize: textTheme.titleMedium?.fontSize,
+      secondaryTextColor: colorScheme.onSurfaceVariant,
+      secondaryBackgroundColor: colorScheme.surface,
+      secondaryTextSize: textTheme.bodyMedium?.fontSize,
+      tertiaryTextColor: colorScheme.onSurfaceVariant,
+      tertiaryBackgroundColor: colorScheme.surface,
+      tertiaryTextSize: textTheme.labelSmall?.fontSize,
+    );
+  }
+
+  /// The background color for the main ad container.
+  final Color mainBackgroundColor;
+
+  /// The corner radius for the ad container.
+  final double cornerRadius;
+
+  /// The text color for the call-to-action button.
+  final Color callToActionTextColor;
+
+  /// The background color for the call-to-action button.
+  final Color callToActionBackgroundColor;
+
+  /// The font size for the call-to-action text.
+  final double? callToActionTextSize;
+
+  /// The text color for the primary text (e.g., ad headline).
+  final Color primaryTextColor;
+
+  /// The background color for the primary text.
+  final Color primaryBackgroundColor;
+
+  /// The font size for the primary text.
+  final double? primaryTextSize;
+
+  /// The text color for the secondary text (e.g., ad body).
+  final Color secondaryTextColor;
+
+  /// The background color for the secondary text.
+  final Color secondaryBackgroundColor;
+
+  /// The font size for the secondary text.
+  final double? secondaryTextSize;
+
+  /// The text color for the tertiary text (e.g., ad attribution).
+  final Color tertiaryTextColor;
+
+  /// The background color for the tertiary text.
+  final Color tertiaryBackgroundColor;
+
+  /// The font size for the tertiary text.
+  final double? tertiaryTextSize;
+
+  @override
+  List<Object?> get props => [
+        mainBackgroundColor,
+        cornerRadius,
+        callToActionTextColor,
+        callToActionBackgroundColor,
+        callToActionTextSize,
+        primaryTextColor,
+        primaryBackgroundColor,
+        primaryTextSize,
+        secondaryTextColor,
+        secondaryBackgroundColor,
+        secondaryTextSize,
+        tertiaryTextColor,
+        tertiaryBackgroundColor,
+        tertiaryTextSize,
+      ];
+}