refactor: Introduce pre-consume quota and unify relay handlers

This commit introduces a major architectural refactoring to improve quota management, centralize logging, and streamline the relay handling logic.

Key changes:
- **Pre-consume Quota:** Implements a new mechanism to check and reserve user quota *before* making the request to the upstream provider. This ensures more accurate quota deduction and prevents users from exceeding their limits due to concurrent requests.

- **Unified Relay Handlers:** Refactors the relay logic to use generic handlers (e.g., `ChatHandler`, `ImageHandler`) instead of provider-specific implementations. This significantly reduces code duplication and simplifies adding new channels.

- **Centralized Logger:** A new dedicated `logger` package is introduced, and all system logging calls are migrated to use it, moving this responsibility out of the `common` package.

- **Code Reorganization:** DTOs are generalized (e.g., `dalle.go` -> `openai_image.go`) and utility code is moved to more appropriate packages (e.g., `common/http.go` -> `service/http.go`) for better code structure.

relay/channel/dify/relay-dify.go

@@ -11,6 +11,7 @@ import (
 	"one-api/common"
 	"one-api/constant"
 	"one-api/dto"
+	"one-api/logger"
 	relaycommon "one-api/relay/common"
 	"one-api/relay/helper"
 	"one-api/service"
@@ -36,14 +37,14 @@ func uploadDifyFile(c *gin.Context, info *relaycommon.RelayInfo, user string, me
 		// Decode base64 string
 		decodedData, err := base64.StdEncoding.DecodeString(base64Data)
 		if err != nil {
-			common.SysError("failed to decode base64: " + err.Error())
+			logger.SysError("failed to decode base64: " + err.Error())
 			return nil
 		}
 
 		// Create temporary file
 		tempFile, err := os.CreateTemp("", "dify-upload-*")
 		if err != nil {
-			common.SysError("failed to create temp file: " + err.Error())
+			logger.SysError("failed to create temp file: " + err.Error())
 			return nil
 		}
 		defer tempFile.Close()
@@ -51,7 +52,7 @@ func uploadDifyFile(c *gin.Context, info *relaycommon.RelayInfo, user string, me
 
 		// Write decoded data to temp file
 		if _, err := tempFile.Write(decodedData); err != nil {
-			common.SysError("failed to write to temp file: " + err.Error())
+			logger.SysError("failed to write to temp file: " + err.Error())
 			return nil
 		}
 
@@ -61,7 +62,7 @@ func uploadDifyFile(c *gin.Context, info *relaycommon.RelayInfo, user string, me
 
 		// Add user field
 		if err := writer.WriteField("user", user); err != nil {
-			common.SysError("failed to add user field: " + err.Error())
+			logger.SysError("failed to add user field: " + err.Error())
 			return nil
 		}
 
@@ -74,13 +75,13 @@ func uploadDifyFile(c *gin.Context, info *relaycommon.RelayInfo, user string, me
 		// Create form file
 		part, err := writer.CreateFormFile("file", fmt.Sprintf("image.%s", strings.TrimPrefix(mimeType, "image/")))
 		if err != nil {
-			common.SysError("failed to create form file: " + err.Error())
+			logger.SysError("failed to create form file: " + err.Error())
 			return nil
 		}
 
 		// Copy file content to form
 		if _, err = io.Copy(part, bytes.NewReader(decodedData)); err != nil {
-			common.SysError("failed to copy file content: " + err.Error())
+			logger.SysError("failed to copy file content: " + err.Error())
 			return nil
 		}
 		writer.Close()
@@ -88,7 +89,7 @@ func uploadDifyFile(c *gin.Context, info *relaycommon.RelayInfo, user string, me
 		// Create HTTP request
 		req, err := http.NewRequest("POST", uploadUrl, body)
 		if err != nil {
-			common.SysError("failed to create request: " + err.Error())
+			logger.SysError("failed to create request: " + err.Error())
 			return nil
 		}
 
@@ -99,7 +100,7 @@ func uploadDifyFile(c *gin.Context, info *relaycommon.RelayInfo, user string, me
 		client := service.GetHttpClient()
 		resp, err := client.Do(req)
 		if err != nil {
-			common.SysError("failed to send request: " + err.Error())
+			logger.SysError("failed to send request: " + err.Error())
 			return nil
 		}
 		defer resp.Body.Close()
@@ -109,7 +110,7 @@ func uploadDifyFile(c *gin.Context, info *relaycommon.RelayInfo, user string, me
 			Id string `json:"id"`
 		}
 		if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
-			common.SysError("failed to decode response: " + err.Error())
+			logger.SysError("failed to decode response: " + err.Error())
 			return nil
 		}
 
@@ -219,7 +220,7 @@ func difyStreamHandler(c *gin.Context, info *relaycommon.RelayInfo, resp *http.R
 		var difyResponse DifyChunkChatCompletionResponse
 		err := json.Unmarshal([]byte(data), &difyResponse)
 		if err != nil {
-			common.SysError("error unmarshalling stream response: " + err.Error())
+			logger.SysError("error unmarshalling stream response: " + err.Error())
 			return true
 		}
 		var openaiResponse dto.ChatCompletionsStreamResponse
@@ -239,7 +240,7 @@ func difyStreamHandler(c *gin.Context, info *relaycommon.RelayInfo, resp *http.R
 		}
 		err = helper.ObjectData(c, openaiResponse)
 		if err != nil {
-			common.SysError(err.Error())
+			logger.SysError(err.Error())
 		}
 		return true
 	})
@@ -258,7 +259,7 @@ func difyHandler(c *gin.Context, info *relaycommon.RelayInfo, resp *http.Respons
 	if err != nil {
 		return nil, types.NewError(err, types.ErrorCodeBadResponseBody)
 	}
-	common.CloseResponseBodyGracefully(resp)
+	service.CloseResponseBodyGracefully(resp)
 	err = json.Unmarshal(responseBody, &difyResponse)
 	if err != nil {
 		return nil, types.NewError(err, types.ErrorCodeBadResponseBody)