fix: Refactor relay/channel, upgrade deps, improve request handling and error messages.

* Updated relay/channel/gemini package to use gin-gonic/gin for routing
* Added timeouts, environment variable for proxy, and error handling for HTTP clients in relay/util/init.go
* Improved error handling, URL path cases, and channel selection logic in middleware/distributor.go
* Added Content-Type header, closed request bodies, and added context to requests in relay/channel/common.go
* Upgraded various dependencies in go.mod
* Modified the GetRequestURL method in relay/channel/gemini/adaptor.go to include a "key" parameter in the URL and set a default version of "v1beta"
* Added io and net/http packages in relay/channel/gemini/adaptor.go and relay/channel/gemini/main.go
* Added a struct for GeminiStreamResp and modified response handling in relay/channel/gemini/main.go
* Imported packages for io and net/http added, gin-gonic/gin package added, and error handling improved in relay/channel/gemini/main.go

middleware/distributor.go

@@ -44,7 +44,7 @@ func Distribute() func(c *gin.Context) {
 			var modelRequest ModelRequest
 			err := common.UnmarshalBodyReusable(c, &modelRequest)
 			if err != nil {
-				abortWithMessage(c, http.StatusBadRequest, "无效的请求")
+				abortWithMessage(c, http.StatusBadRequest, fmt.Sprintf("无效的请求: %+v", err))
 				return
 			}
 			if strings.HasPrefix(c.Request.URL.Path, "/v1/moderations") {