feat: Refactor remaining icon usage to utilize AppIcons class across multiple screens and update icon references

lib/app_icons.dart

···
 
 class AppIcons {
   // Material Icons
+  static const IconData edit = Icons.edit;
+  static const IconData sort = Icons.sort;
   static const IconData person = Icons.person;
   static const IconData accountCircle = Icons.account_circle;
   static const IconData close = Icons.close;
···
   static const IconData notifications = Icons.notifications;
   static const IconData search = Icons.search;
   static const IconData settings = Icons.settings;
+  static const IconData photoLibrary = Icons.photo_library;
+  static const IconData moreVertical = Icons.more_vert;
   // FontAwesome Icons
   static const IconData house = FontAwesomeIcons.house;
   static const IconData magnifyingGlass = FontAwesomeIcons.magnifyingGlass;
···
   static const IconData arrowUpFromBracket = FontAwesomeIcons.arrowUpFromBracket;
   static const IconData bars = FontAwesomeIcons.bars;
   static const IconData arrowRightFromBracket = FontAwesomeIcons.arrowRightFromBracket;
-  static const IconData checkCircle = FontAwesomeIcons.checkCircle;
+  static const IconData checkCircle = FontAwesomeIcons.circleCheck;
 }

lib/screens/create_gallery_page.dart

···
 import 'package:flutter/services.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:grain/api.dart';
+import 'package:grain/app_icons.dart';
 import 'package:grain/models/gallery.dart';
 import 'package:grain/providers/profile_provider.dart';
 import 'package:grain/widgets/app_button.dart';
···
                       child: AppButton(
                         label: 'Upload photos',
                         onPressed: _pickImages,
-                        icon: Icons.photo_library,
+                        icon: AppIcons.photoLibrary,
                         variant: AppButtonVariant.primary,
                         height: 40,
                         fontSize: 15,
···
                                 borderRadius: BorderRadius.circular(4),
                               ),
                               child: Icon(
-                                Icons.check_circle,
+                                AppIcons.checkCircle,
                                 color: theme.colorScheme.onSecondary,
                                 size: 16,
                               ),
···
                                 shape: BoxShape.circle,
                               ),
                               padding: const EdgeInsets.all(4),
-                              child: const Icon(Icons.close, color: Colors.white, size: 20),
+                              child: const Icon(AppIcons.close, color: Colors.white, size: 20),
                             ),
                           ),
                         ),

lib/screens/explore_page.dart

···
 
 import 'package:flutter/material.dart';
 import 'package:grain/api.dart';
+import 'package:grain/app_icons.dart';
 import 'package:grain/models/profile.dart';
 import 'package:grain/widgets/app_image.dart';
 import 'package:grain/widgets/plain_text_field.dart';
···
               : CircleAvatar(
                   radius: 16,
                   backgroundColor: theme.colorScheme.surfaceContainerHighest,
-                  child: Icon(Icons.account_circle, color: theme.iconTheme.color),
+                  child: Icon(AppIcons.accountCircle, color: theme.iconTheme.color),
                 ),
           title: Text(
             profile.displayName?.isNotEmpty == true ? profile.displayName! : '@${profile.handle}',

lib/screens/gallery_action_sheet.dart

···
 import 'package:flutter/material.dart';
+import 'package:grain/app_icons.dart';
 
 class GalleryActionSheet extends StatelessWidget {
   final VoidCallback? onEditDetails;
···
         mainAxisSize: MainAxisSize.min,
         children: [
           ListTile(
-            leading: const Icon(Icons.edit),
+            leading: Icon(AppIcons.edit),
             title: const Text('Edit details'),
             onTap: () {
               Navigator.of(context).pop();
···
             },
           ),
           ListTile(
-            leading: const Icon(Icons.photo_library),
+            leading: Icon(AppIcons.photoLibrary),
             title: const Text('Edit photos'),
             onTap: () {
               Navigator.of(context).pop();
···
             },
           ),
           ListTile(
-            leading: const Icon(Icons.sort),
+            leading: Icon(AppIcons.sort),
             title: const Text('Edit sort order'),
             onTap: () {
               Navigator.of(context).pop();
···
             },
           ),
           ListTile(
-            leading: const Icon(Icons.delete, color: Colors.red),
+            leading: Icon(AppIcons.delete, color: Colors.red),
             title: const Text('Delete gallery', style: TextStyle(color: Colors.red)),
             onTap: () async {
               Navigator.of(context).pop();

lib/screens/gallery_edit_photos_sheet.dart

···
 import 'package:flutter/services.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:grain/api.dart';
+import 'package:grain/app_icons.dart';
 import 'package:grain/models/gallery_photo.dart';
 import 'package:grain/providers/gallery_cache_provider.dart';
 import 'package:grain/widgets/app_button.dart';
···
                               clipBehavior: Clip.antiAlias,
                               child: photo.thumb != null && photo.thumb!.isNotEmpty
                                   ? AppImage(url: photo.thumb!, fit: BoxFit.cover)
-                                  : const Icon(Icons.photo, size: 48),
+                                  : const Icon(AppIcons.photo, size: 48),
                             ),
                             Positioned(
                               top: 8,
···
                                             valueColor: AlwaysStoppedAnimation<Color>(Colors.white),
                                           ),
                                         )
-                                      : const Icon(Icons.close, color: Colors.white, size: 20),
+                                      : const Icon(AppIcons.close, color: Colors.white, size: 20),
                                 ),
                               ),
                             ),

lib/screens/gallery_page.dart

···
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:grain/api.dart';
+import 'package:grain/app_icons.dart';
 import 'package:grain/models/gallery_photo.dart';
 import 'package:grain/providers/gallery_cache_provider.dart';
 import 'package:grain/providers/profile_provider.dart';
···
             actions: [
               if (gallery.creator?.did == widget.currentUserDid)
                 IconButton(
-                  icon: const Icon(Icons.more_vert),
+                  icon: const Icon(AppIcons.moreVertical),
                   tooltip: 'Gallery Actions',
                   onPressed: () async {
                     showModalBottomSheet(
···
                                   (gallery.creator == null ||
                                       (gallery.creator!.avatar?.isNotEmpty != true))
                                   ? Icon(
-                                      Icons.account_circle,
+                                      AppIcons.accountCircle,
                                       size: 24,
                                       color: theme.colorScheme.onSurface.withOpacity(0.4),
                                     )