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.

service/midjourney.go

@@ -9,6 +9,7 @@ import (
 	"one-api/common"
 	"one-api/constant"
 	"one-api/dto"
+	"one-api/logger"
 	relayconstant "one-api/relay/constant"
 	"one-api/setting"
 	"strconv"
@@ -212,7 +213,7 @@ func DoMidjourneyHttpRequest(c *gin.Context, timeout time.Duration, fullRequestU
 	defer cancel()
 	resp, err := GetHttpClient().Do(req)
 	if err != nil {
-		common.SysError("do request failed: " + err.Error())
+		logger.SysError("do request failed: " + err.Error())
 		return MidjourneyErrorWithStatusCodeWrapper(constant.MjErrorUnknown, "do_request_failed", http.StatusInternalServerError), nullBytes, err
 	}
 	statusCode := resp.StatusCode
@@ -233,7 +234,7 @@ func DoMidjourneyHttpRequest(c *gin.Context, timeout time.Duration, fullRequestU
 	if err != nil {
 		return MidjourneyErrorWithStatusCodeWrapper(constant.MjErrorUnknown, "read_response_body_failed", statusCode), nullBytes, err
 	}
-	common.CloseResponseBodyGracefully(resp)
+	CloseResponseBodyGracefully(resp)
 	respStr := string(responseBody)
 	log.Printf("respStr: %s", respStr)
 	if respStr == "" {