feat: 算力引擎 Go 后端核心（new-api）

- 统一 OpenAI 兼容 /v1 中继 + 渠道/额度/令牌/流水
- 各领域包：relay 模型网关、model 数据层、controller 管理 API

relaykit/go.mod

@@ -0,0 +1,23 @@
+module github.com/QuantumNous/new-api/relaykit
+
+go 1.25.1
+
+require (
+	github.com/google/uuid v1.6.0
+	github.com/samber/lo v1.53.0
+	github.com/stretchr/testify v1.11.1
+	github.com/tidwall/gjson v1.19.0
+	github.com/tidwall/sjson v1.2.5
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
+	github.com/kr/pretty v0.3.1 // indirect
+	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
+	github.com/rogpeppe/go-internal v1.10.0 // indirect
+	github.com/tidwall/match v1.1.1 // indirect
+	github.com/tidwall/pretty v1.2.0 // indirect
+	golang.org/x/text v0.35.0 // indirect
+	gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)