Refactor codebase, introduce relaymode package, update constants and improve consistency

- Refactor constant definitions and organization
- Clean up package level variables and functions
- Introduce new `relaymode` and `apitype` packages for constant definitions
- Refactor and simplify code in several packages including `openai`, `relay/channel/baidu`, `relay/util`, `relay/controller`, `relay/channeltype`
- Add helper functions in `relay/channeltype` package to convert channel type constants to corresponding API type constants
- Remove deprecated functions such as `ResponseText2Usage` from `relay/channel/openai/helper.go`
- Modify code in `relay/util/validation.go` and related files to use new `validator.ValidateTextRequest` function
- Rename `util` package to `relaymode` and update related imports in several packages

controller/misc.go

@@ -23,6 +23,7 @@ func GetStatus(c *gin.Context) {
 			"email_verification":  config.EmailVerificationEnabled,
 			"github_oauth":        config.GitHubOAuthEnabled,
 			"github_client_id":    config.GitHubClientId,
+			"lark_client_id":      config.LarkClientId,
 			"system_name":         config.SystemName,
 			"logo":                config.Logo,
 			"footer_html":         config.Footer,