feat(markdown): Add syntax highlighting with flutter_highlight

lib/shared/widgets/markdown/markdown_config.dart

@@ -5,6 +5,9 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
+import 'package:flutter_highlight/flutter_highlight.dart';
+import 'package:flutter_highlight/themes/atom-one-dark.dart';
+import 'package:flutter_highlight/themes/github.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:flutter_math_fork/flutter_math.dart';
 import 'package:gpt_markdown/gpt_markdown.dart';
@@ -98,7 +101,13 @@ class ConduitMarkdown {
         ? 'plaintext'
         : language.trim();
 
-    // Match GitHub/Atom theme colors for code block container
+    // Map common language aliases to highlight.js recognized names
+    final highlightLanguage = _mapLanguage(normalizedLanguage);
+
+    // Use Atom One Dark for dark mode, GitHub for light mode
+    final highlightTheme = isDark ? atomOneDarkTheme : githubTheme;
+
+    // Match theme colors for code block container
     final codeBackground = isDark
         ? const Color(0xFF282c34) // Atom One Dark background
         : const Color(0xFFfafbfc); // GitHub light background
@@ -135,10 +144,12 @@ class ConduitMarkdown {
           SingleChildScrollView(
             scrollDirection: Axis.horizontal,
             padding: const EdgeInsets.all(Spacing.md),
-            child: SelectableText(
+            child: HighlightView(
               code,
-              style: AppTypography.codeStyle.copyWith(
-                color: theme.codeText,
+              language: highlightLanguage,
+              theme: highlightTheme,
+              padding: EdgeInsets.zero,
+              textStyle: AppTypography.codeStyle.copyWith(
                 fontFamily: AppTypography.monospaceFontFamily,
               ),
             ),
@@ -148,6 +159,34 @@ class ConduitMarkdown {
     );
   }
 
+  /// Maps common language names/aliases to highlight.js recognized names.
+  static String _mapLanguage(String language) {
+    final lower = language.toLowerCase();
+
+    // Common language aliases mapping
+    const languageMap = <String, String>{
+      'js': 'javascript',
+      'ts': 'typescript',
+      'py': 'python',
+      'rb': 'ruby',
+      'sh': 'bash',
+      'shell': 'bash',
+      'zsh': 'bash',
+      'yml': 'yaml',
+      'dockerfile': 'docker',
+      'kt': 'kotlin',
+      'cs': 'csharp',
+      'c++': 'cpp',
+      'objc': 'objectivec',
+      'objective-c': 'objectivec',
+      'txt': 'plaintext',
+      'text': 'plaintext',
+      'md': 'markdown',
+    };
+
+    return languageMap[lower] ?? lower;
+  }
+
   static Widget _buildImage(
     BuildContext context,
     Uri uri,

pubspec.lock

@@ -494,6 +494,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "3.0.0"
+  flutter_highlight:
+    dependency: "direct main"
+    description:
+      name: flutter_highlight
+      sha256: "7b96333867aa07e122e245c033b8ad622e4e3a42a1a2372cbb098a2541d8782c"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.7.0"
   flutter_lints:
     dependency: "direct dev"
     description:
@@ -709,6 +717,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.3.2"
+  highlight:
+    dependency: transitive
+    description:
+      name: highlight
+      sha256: "5353a83ffe3e3eca7df0abfb72dcf3fa66cc56b953728e7113ad4ad88497cf21"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.7.0"
   hive_ce:
     dependency: "direct main"
     description:

pubspec.yaml

@@ -78,6 +78,7 @@ dependencies:
   flutter_svg: ^2.2.3
   html_unescape: ^2.0.0
   home_widget: ^0.8.1
+  flutter_highlight: ^0.7.0
   
   # Clipboard functionality is available through flutter/services (part of Flutter SDK)