refactor: 替换硬编码文本为多语言配置

1. 替换分销等级页标题拼接的硬编码语言文本
2. 替换AI聊天页面的硬编码提示文本为多语言key
3. 新增完整的多语言翻译配置项

pages_tool/ai-chat/ai-chat-message.vue

@@ -1426,7 +1426,7 @@ _handleStreamError(msg) {
       }
       this.isFetchingHistory = true;
       this.isLoadingHistory = true;
-      this.loadingText = '加载历史消息中...';
+      this.loadingText = this.$lang('aiChat.loadingHistory');
 
       try {
         const response = await aiService.getConversationHistory({
@@ -1480,7 +1480,7 @@ _handleStreamError(msg) {
       } finally {
         this.isLoadingHistory = false;
         this.isFetchingHistory = false;
-        this.loadingText = '加载更多历史消息';
+        this.loadingText = this.$lang('aiChat.loadMoreHistory');
       }
     },
     // 显示更多工具
@@ -1688,7 +1688,7 @@ _handleStreamError(msg) {
       try {
         if (navigator.clipboard && navigator.clipboard.writeText) {
           navigator.clipboard.writeText(finalText).then(() => {
-            uni.showToast({ title: selectedText ? '已复制选中内容' : '已复制', icon: 'success' })
+            uni.showToast({ title: selectedText ? this.$lang('aiChat.copySelected') : this.$lang('aiChat.copySuccess'), icon: 'success' })
           }).catch(() => {
             this._fallbackCopyH5(finalText)
           })