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/go.mod

@@ -5,14 +5,19 @@ go 1.26
 require (
 	github.com/gin-contrib/cors v1.7.5
 	github.com/gin-gonic/gin v1.10.1
+	github.com/go-ldap/ldap/v3 v3.4.13
+	github.com/go-sql-driver/mysql v1.10.0
 	github.com/golang-jwt/jwt/v5 v5.2.2
+	github.com/jackc/pgx/v5 v5.9.2
 	github.com/joho/godotenv v1.5.1
+	github.com/redis/go-redis/v9 v9.19.0
 	golang.org/x/crypto v0.48.0
 	gorm.io/driver/sqlite v1.5.7
 	gorm.io/gorm v1.26.0
 )
 
 require (
+	filippo.io/edwards25519 v1.2.0 // indirect
 	github.com/Azure/go-ntlmssp v0.1.0 // indirect
 	github.com/bytedance/sonic v1.13.2 // indirect
 	github.com/bytedance/sonic/loader v0.2.4 // indirect
@@ -21,12 +26,14 @@ require (
 	github.com/gabriel-vasile/mimetype v1.4.8 // indirect
 	github.com/gin-contrib/sse v1.0.0 // indirect
 	github.com/go-asn1-ber/asn1-ber v1.5.8-0.20250403174932-29230038a667 // indirect
-	github.com/go-ldap/ldap/v3 v3.4.13 // indirect
 	github.com/go-playground/locales v0.14.1 // indirect
 	github.com/go-playground/universal-translator v0.18.1 // indirect
 	github.com/go-playground/validator/v10 v10.26.0 // indirect
 	github.com/goccy/go-json v0.10.5 // indirect
 	github.com/google/uuid v1.6.0 // indirect
+	github.com/jackc/pgpassfile v1.0.0 // indirect
+	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
+	github.com/jackc/puddle/v2 v2.2.2 // indirect
 	github.com/jinzhu/inflection v1.0.0 // indirect
 	github.com/jinzhu/now v1.1.5 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
@@ -38,12 +45,12 @@ require (
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
 	github.com/modern-go/reflect2 v1.0.2 // indirect
 	github.com/pelletier/go-toml/v2 v2.2.3 // indirect
-	github.com/redis/go-redis/v9 v9.19.0 // indirect
 	github.com/twitchyliquid64/golang-asm v0.15.1 // indirect
 	github.com/ugorji/go/codec v1.2.12 // indirect
 	go.uber.org/atomic v1.11.0 // indirect
 	golang.org/x/arch v0.15.0 // indirect
 	golang.org/x/net v0.50.0 // indirect
+	golang.org/x/sync v0.19.0 // indirect
 	golang.org/x/sys v0.41.0 // indirect
 	golang.org/x/text v0.34.0 // indirect
 	google.golang.org/protobuf v1.36.6 // indirect