refactor: Replace hardcoded monospace font with AppTypography constant

- Updated multiple instances of the 'monospace' font family to use AppTypography.monospaceFontFamily for consistency across the application.
- This change enhances maintainability and ensures a unified typography approach throughout the app.

lib/core/services/user_friendly_error_handler.dart

@@ -456,7 +456,7 @@ class ErrorCard extends StatelessWidget {
                     child: SelectableText(
                       technicalDetails!,
                       style: const TextStyle(
-                        fontFamily: 'monospace',
+                        fontFamily: AppTypography.monospaceFontFamily,
                         fontSize: AppTypography.labelMedium,
                       ),
                     ),
@@ -539,7 +539,7 @@ class ErrorDialog extends StatelessWidget {
                 SelectableText(
                   technicalDetails!,
                   style: const TextStyle(
-                    fontFamily: 'monospace',
+                    fontFamily: AppTypography.monospaceFontFamily,
                     fontSize: AppTypography.labelMedium,
                   ),
                 ),

lib/features/auth/views/authentication_page.dart

@@ -288,7 +288,7 @@ class _AuthenticationPageState extends ConsumerState<AuthenticationPage> {
                   hostText,
                   style: context.conduitTheme.bodySmall?.copyWith(
                     color: context.conduitTheme.textSecondary,
-                    fontFamily: 'monospace',
+                    fontFamily: AppTypography.monospaceFontFamily,
                   ),
                 ),
               ],

lib/features/auth/views/connection_issue_page.dart

@@ -151,7 +151,7 @@ class _ConnectionIssuePageState extends ConsumerState<ConnectionIssuePage> {
           textAlign: TextAlign.center,
           style: context.conduitTheme.bodyMedium?.copyWith(
             color: context.conduitTheme.textPrimary,
-            fontFamily: 'monospace',
+            fontFamily: AppTypography.monospaceFontFamily,
           ),
         ),
         const SizedBox(height: Spacing.xs),

lib/features/auth/views/server_connection_page.dart

@@ -721,7 +721,7 @@ class _ServerConnectionPageState extends ConsumerState<ServerConnectionPage> {
                   entry.value,
                   style: context.conduitTheme.bodySmall?.copyWith(
                     color: context.conduitTheme.textSecondary,
-                    fontFamily: 'monospace',
+                    fontFamily: AppTypography.monospaceFontFamily,
                   ),
                   overflow: TextOverflow.ellipsis,
                 ),

lib/features/chat/widgets/assistant_message_widget.dart

@@ -385,7 +385,7 @@ class _AssistantMessageWidgetState extends ConsumerState<AssistantMessageWidget>
                           style: TextStyle(
                             fontSize: AppTypography.bodySmall,
                             color: theme.textSecondary,
-                            fontFamily: 'monospace',
+                            fontFamily: AppTypography.monospaceFontFamily,
                             height: 1.35,
                           ),
                         ),
@@ -407,7 +407,7 @@ class _AssistantMessageWidgetState extends ConsumerState<AssistantMessageWidget>
                           style: TextStyle(
                             fontSize: AppTypography.bodySmall,
                             color: theme.textSecondary,
-                            fontFamily: 'monospace',
+                            fontFamily: AppTypography.monospaceFontFamily,
                             height: 1.35,
                           ),
                         ),
@@ -1207,7 +1207,7 @@ class _AssistantMessageWidgetState extends ConsumerState<AssistantMessageWidget>
                     style: TextStyle(
                       fontSize: AppTypography.bodySmall,
                       color: theme.textSecondary,
-                      fontFamily: 'monospace',
+                      fontFamily: AppTypography.monospaceFontFamily,
                       height: 1.4,
                     ),
                   ),
@@ -1994,7 +1994,7 @@ class CodeExecutionListView extends StatelessWidget {
                       child: SelectableText(
                         execution.code!,
                         style: const TextStyle(
-                          fontFamily: 'monospace',
+                          fontFamily: AppTypography.monospaceFontFamily,
                           height: 1.4,
                         ),
                       ),

lib/shared/theme/theme_extensions.dart

@@ -1168,7 +1168,7 @@ class ConduitShadows {
 class AppTypography {
   // Primary UI font now uses the platform default system font
   static const String fontFamily = '';
-  static const String monospaceFontFamily = 'SF Mono';
+  static const String monospaceFontFamily = 'monospace';
 
   // Letter spacing values - Enhanced for better readability
   static const double letterSpacingTight = -0.5;