feat(user): add local avatar management flow

inc/helpers/user-center-renderers/profile-header.php

@@ -94,7 +94,10 @@ extract($context, EXTR_SKIP); // phpcs:ignore WordPress.PHP.DontExtract.extract_
 			<button type="button" id="aksrt-upload-avatar-btn" class="btn-ghost btn-sm">
 				<i class="fas fa-camera" aria-hidden="true"></i> <span><?php esc_html_e('更换头像', 'aksrt'); ?></span>
 			</button>
-			<input type="file" id="aksrt-avatar-file-input" accept="image/jpeg,image/png,image/webp,image/gif" hidden>
+				<input type="file" id="aksrt-avatar-file-input" accept="image/jpeg,image/png,image/webp,image/gif" hidden>
+				<button type="button" id="aksrt-remove-avatar-btn" class="btn-ghost btn-sm"<?php echo get_user_meta($user_id, 'aksrt_avatar_attachment_id', true) ? '' : ' hidden'; ?>>
+					<i class="fas fa-undo" aria-hidden="true"></i> <span><?php esc_html_e('恢复默认头像', 'aksrt'); ?></span>
+				</button>
 			<?php endif; ?>
 			<a href="<?php echo esc_url(aksrt_get_user_home_url()); ?>" class="btn-ghost btn-sm">
 				<i class="fas fa-map-marker-alt" aria-hidden="true"></i> <?php esc_html_e('我的主页', 'aksrt'); ?>