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.

model/channel_cache.go

@@ -6,6 +6,7 @@ import (
 	"math/rand"
 	"one-api/common"
 	"one-api/constant"
+	"one-api/logger"
 	"one-api/setting"
 	"one-api/setting/ratio_setting"
 	"sort"
@@ -84,13 +85,13 @@ func InitChannelCache() {
 	}
 	channelsIDM = newChannelId2channel
 	channelSyncLock.Unlock()
-	common.SysLog("channels synced from database")
+	logger.SysLog("channels synced from database")
 }
 
 func SyncChannelCache(frequency int) {
 	for {
 		time.Sleep(time.Duration(frequency) * time.Second)
-		common.SysLog("syncing channels from database")
+		logger.SysLog("syncing channels from database")
 		InitChannelCache()
 	}
 }