feat: 实现 PostgreSQL 连接池

- 新增 internal/store/db.go
- 实现 NewPostgresPool(ctx, dsn) 创建连接池
- 添加 pgx/v5 依赖
- 最大连接数设置为 10

backend/go.mod

@@ -1,11 +1,12 @@
 module github.com/hhs/camtalk
 
-go 1.24
+go 1.25.0
 
 require (
 	github.com/gin-gonic/gin v1.10.0
 	github.com/google/uuid v1.6.0
 	github.com/gorilla/websocket v1.5.3
+	github.com/jackc/pgx/v5 v5.10.0
 	github.com/redis/go-redis/v9 v9.20.1
 	github.com/spf13/viper v1.21.0
 	github.com/stretchr/testify v1.11.1
@@ -27,6 +28,9 @@ require (
 	github.com/go-playground/validator/v10 v10.20.0 // indirect
 	github.com/go-viper/mapstructure/v2 v2.4.0 // indirect
 	github.com/goccy/go-json v0.10.2 // 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/json-iterator/go v1.1.12 // indirect
 	github.com/klauspost/cpuid/v2 v2.2.10 // indirect
 	github.com/leodido/go-urn v1.4.0 // indirect
@@ -50,8 +54,9 @@ require (
 	golang.org/x/arch v0.8.0 // indirect
 	golang.org/x/crypto v0.23.0 // indirect
 	golang.org/x/net v0.25.0 // indirect
+	golang.org/x/sync v0.17.0 // indirect
 	golang.org/x/sys v0.30.0 // indirect
-	golang.org/x/text v0.28.0 // indirect
+	golang.org/x/text v0.29.0 // indirect
 	google.golang.org/protobuf v1.34.1 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )