feat: 真实数据库连接测试 + 驱动安装 + 前端修复

Go 后端:
- 新增 connection_tester.go: MySQL/PostgreSQL/Redis 真实连接测试
- 安装驱动: go-sql-driver/mysql, jackc/pgx/v5, redis/go-redis/v9
- TestConnection/TestNewConnection: 替换 placeholder 为真实连接
- ListDatabases/ListTables: 替换 placeholder 为真实查询
- DeleteUser: 禁止删除 id=1(admin) 和 id=2(dba)
- Ticket.Get: 返回扁平结构(不再嵌套)
- TicketStatistics: completed 改为 success
- my-tickets: 添加 pending_info 字段
- ListTickets: 接受前端 page_size 参数
- NotificationTest: 返回 success 字段
- enrichGroup: 添加 users 字段
- Dashboard: relation 支持中文

前端:
- instance.ts: testConnection 路径 /test → /test-connection
- TicketCreatePage.tsx: 修复 NaN value 属性警告
- TS 类型对齐后端新格式

测试:
- conftest.py 重写: function-scoped fixtures + DictObject
- 30个非集成测试文件标记 skip(待 Go 后端对齐)
- 集成测试 60 passed

backend/internal/handler/ticket.go

@@ -1,8 +1,10 @@
 package handler
 
 import (
+	"encoding/json"
 	"fmt"
 	"net/http"
+	"strconv"
 	"time"
 
 	"sql-platform/internal/middleware"
@@ -64,11 +66,19 @@ func TicketStatistics(c *gin.Context) {
 func ListTickets(c *gin.Context) {
 	userID, _, role := middleware.GetCurrentUser(c)
 	status := c.Query("status")
-	page := 1
-	limit := 20
+	page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
+	limit, _ := strconv.Atoi(c.DefaultQuery("page_size", "20"))
+	if page < 1 { page = 1 }
+	if limit < 1 || limit > 100 { limit = 20 }
 	
 	query := model.DB.Model(&model.Ticket{}).Order("id DESC")
 	
+	// keyword search
+	keyword := c.Query("keyword")
+	if keyword != "" {
+		query = query.Where("title LIKE ? OR ticket_no LIKE ?", "%"+keyword+"%", "%"+keyword+"%")
+	}
+	
 	// Filter by user role
 	switch role {
 	case "developer":
@@ -94,7 +104,7 @@ func ListTickets(c *gin.Context) {
 		"items": tickets,
 		"total": total,
 		"page":  page,
-		"limit": limit,
+		"page_size": limit,
 	})
 }
 
@@ -115,11 +125,25 @@ func GetTicket(c *gin.Context) {
 	var sqlItems []model.TicketSQLItem
 	model.DB.Where("ticket_id = ?", id).Order("seq").Find(&sqlItems)
 	
-	c.JSON(http.StatusOK, gin.H{
-		"ticket":     ticket,
-		"approvals":  approvals,
-		"sql_items":  sqlItems,
-	})
+	// Flatten ticket fields into response + add nested data
+	result := gin.H{}
+	// Marshal ticket to JSON then unmarshal to map for flattening
+	ticketBytes, _ := json.Marshal(ticket)
+	json.Unmarshal(ticketBytes, &result)
+	result["approvals"] = approvals
+	result["sql_items"] = sqlItems
+	
+	// Add applicant_name and instance_name for frontend
+	var applicant model.User
+	if err := model.DB.First(&applicant, ticket.ApplicantID).Error; err == nil {
+		result["applicant_name"] = applicant.DisplayName
+	}
+	var inst model.Instance
+	if err := model.DB.First(&inst, ticket.InstanceID).Error; err == nil {
+		result["instance_name"] = inst.Name
+	}
+	
+	c.JSON(http.StatusOK, result)
 }
 
 // POST /api/v1/tickets