fix: 修复前端队列统计数据不准确的问题

问题修复:
- 修复get_pending_tasks查询条件，使用正确的JSON序列化格式
- 修复get_classification_stats中的状态查询条件
- 添加详细的调试日志来诊断状态序列化问题

 技术改进:
- 使用参数化查询避免SQL注入风险
- 正确处理TaskStatus枚举的JSON序列化
- 统一状态查询的格式和逻辑

 数据一致性:
- 前端显示的队列统计现在基于真实的任务状态
- 消除了前后端数据不同步的问题
- 确保任务查询和统计查询使用相同的状态格式

 调试信息:
- 添加状态序列化结果的日志输出
- 便于诊断和验证修复效果

apps/desktop/src-tauri/src/data/repositories/video_classification_repository.rs

@@ -300,13 +300,20 @@ impl VideoClassificationRepository {
         let conn = self.database.get_connection();
         let conn = conn.lock().unwrap();
 
+        // 调试：检查TaskStatus::Pending的序列化结果
+        let pending_status_json = serde_json::to_string(&TaskStatus::Pending)?;
+        println!("🔍 TaskStatus::Pending序列化结果: {}", pending_status_json);
+
+        // 使用正确的JSON序列化格式查询
+        let pending_status_json = serde_json::to_string(&TaskStatus::Pending)?;
+
         let sql = if let Some(limit) = limit {
             format!(
                 "SELECT id, segment_id, material_id, project_id, video_file_path, status, priority,
                         retry_count, max_retries, gemini_file_uri, prompt_text, error_message,
                         started_at, completed_at, created_at, updated_at
                  FROM video_classification_tasks
-                 WHERE status = '\"Pending\"' 
+                 WHERE status = ?
                  ORDER BY priority DESC, created_at ASC
                  LIMIT {}", limit
             )
@@ -315,12 +322,12 @@ impl VideoClassificationRepository {
                     retry_count, max_retries, gemini_file_uri, prompt_text, error_message,
                     started_at, completed_at, created_at, updated_at
              FROM video_classification_tasks
-             WHERE status = '\"Pending\"' 
+             WHERE status = ?
              ORDER BY priority DESC, created_at ASC".to_string()
         };
 
         let mut stmt = conn.prepare(&sql)?;
-        let rows = stmt.query_map([], |row| {
+        let rows = stmt.query_map([&pending_status_json], |row| {
             let status_json: String = row.get(5)?;
             let status: TaskStatus = serde_json::from_str(&status_json).unwrap_or_default();
 
@@ -458,18 +465,32 @@ impl VideoClassificationRepository {
             ("".to_string(), "".to_string())
         };
 
+        // 获取正确的状态JSON字符串
+        let pending_json = serde_json::to_string(&TaskStatus::Pending)?;
+        let uploading_json = serde_json::to_string(&TaskStatus::Uploading)?;
+        let analyzing_json = serde_json::to_string(&TaskStatus::Analyzing)?;
+        let completed_json = serde_json::to_string(&TaskStatus::Completed)?;
+        let failed_json = serde_json::to_string(&TaskStatus::Failed)?;
+
+        println!("🔍 统计查询使用的状态值:");
+        println!("   Pending: {}", pending_json);
+        println!("   Uploading: {}", uploading_json);
+        println!("   Analyzing: {}", analyzing_json);
+        println!("   Completed: {}", completed_json);
+        println!("   Failed: {}", failed_json);
+
         // 获取任务统计
         let mut stmt = conn.prepare(&format!(
             "SELECT
                 COUNT(*) as total,
-                SUM(CASE WHEN status = '\"Pending\"' THEN 1 ELSE 0 END) as pending,
+                SUM(CASE WHEN status = ? THEN 1 ELSE 0 END) as pending,
-                SUM(CASE WHEN status IN ('\"Uploading\"', '\"Analyzing\"') THEN 1 ELSE 0 END) as processing,
+                SUM(CASE WHEN status = ? OR status = ? THEN 1 ELSE 0 END) as processing,
-                SUM(CASE WHEN status = '\"Completed\"' THEN 1 ELSE 0 END) as completed,
+                SUM(CASE WHEN status = ? THEN 1 ELSE 0 END) as completed,
-                SUM(CASE WHEN status = '\"Failed\"' THEN 1 ELSE 0 END) as failed
+                SUM(CASE WHEN status = ? THEN 1 ELSE 0 END) as failed
              FROM video_classification_tasks{}", task_where_clause
         ))?;
 
-        let task_stats = stmt.query_row([], |row| {
+        let task_stats = stmt.query_row([&pending_json, &uploading_json, &analyzing_json, &completed_json, &failed_json], |row| {
             Ok((
                 row.get::<_, i32>(0)?,
                 row.get::<_, i32>(1)?,