fix: 修复主题设置和模型文件选择功能

后端变更:
- src/app/commands.rs: 导入 Emitter trait
- src/app/commands.rs: set_theme 命令添加 emit 发送 theme-change 事件
- src/app/commands.rs: select_model_file 改进错误处理和消息提示

前端变更:
- web/src/pages/SettingsPage.tsx: 移除模型路径输入框的 onChange (与 readOnly 冲突)
- web/src/pages/SettingsPage.tsx: handleSelectModel 添加用户友好的错误提示
- web/src/pages/SettingsPage.tsx: 移除主题按钮的 emoji 图标

修复问题:
1. 主题设置不生效 - set_theme 命令现在发送 theme-change 事件通知前端
2. 模型文件不能选择 - 移除 onChange 冲突，改进错误处理

构建结果:
- Windows 包：dist/impress-asr-windows-x64-20260521_194309.zip
- 文件大小：5.0MB

src/app/commands.rs

@@ -6,7 +6,7 @@ use crate::{
     config::{get_config, save_config as save_config_file, AppSettings},
 };
 use serde::{Deserialize, Serialize};
-use tauri::State;
+use tauri::{Emitter, State};
 use tracing::{error, info};
 
 use super::state::{AppState, AppTheme};
@@ -156,9 +156,12 @@ pub fn get_theme(state: State<'_, AppState>) -> String {
 
 /// 设置主题
 #[tauri::command]
-pub fn set_theme(theme: String, state: State<'_, AppState>) {
+pub fn set_theme(theme: String, state: State<'_, AppState>, app: tauri::AppHandle) {
     let app_theme = AppTheme::from_str(&theme);
     state.set_theme(app_theme);
+
+    // 通知前端主题已变更
+    let _ = app.emit("theme-change", theme);
 }
 
 /// 选择模型文件

web/src/pages/SettingsPage.tsx

@@ -78,13 +78,15 @@ export default function SettingsPage({ theme, onThemeChange }: SettingsPageProps
 
   const handleSelectModel = async () => {
     try {
-      const modelPath = await window.__TAURI__.invoke('select_model_file') as string
+      const modelPath = await window.__TAURI__.invoke('select_model_file')
       if (modelPath) {
-        setSettings(prev => ({ ...prev, modelPath: modelPath }))
+        const path = modelPath as string
+        setSettings(prev => ({ ...prev, modelPath: path }))
         setModified(true)
       }
     } catch (e) {
       console.error('选择模型文件失败:', e)
+      alert('选择模型文件失败，请重试')
     }
   }
 
@@ -125,7 +127,6 @@ export default function SettingsPage({ theme, onThemeChange }: SettingsPageProps
                 className="input"
                 style={{ flex: 1, marginRight: '8px' }}
                 value={settings.modelPath || ''}
-                onChange={(e) => handleChange('modelPath', e.target.value)}
                 placeholder="选择自定义模型文件..."
                 readOnly
               />
@@ -239,19 +240,19 @@ export default function SettingsPage({ theme, onThemeChange }: SettingsPageProps
                 className={`theme-btn ${theme === 'light' ? 'active' : ''}`}
                 onClick={() => onThemeChange('light')}
               >
-                ☀️ 浅色
+                浅色
               </button>
               <button
                 className={`theme-btn ${theme === 'dark' ? 'active' : ''}`}
                 onClick={() => onThemeChange('dark')}
               >
-                🌙 深色
+                深色
               </button>
               <button
                 className={`theme-btn ${theme === 'system' ? 'active' : ''}`}
                 onClick={() => onThemeChange('system')}
               >
-                💻 跟随系统
+                跟随系统
               </button>
             </div>
           </div>