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.

types/request_meta.go

@@ -0,0 +1,45 @@
+package types
+
+type FileType string
+
+const (
+	FileTypeImage FileType = "image" // Image file type
+	FileTypeAudio FileType = "audio" // Audio file type
+	FileTypeVideo FileType = "video" // Video file type
+	FileTypeFile  FileType = "file"  // Generic file type
+)
+
+type TokenType string
+
+const (
+	TokenTypeTextNumber TokenType = "text_number" // Text or number tokens
+	TokenTypeTokenizer  TokenType = "tokenizer"   // Tokenizer tokens
+	TokenTypeImage      TokenType = "image"       // Image tokens
+)
+
+type TokenCountMeta struct {
+	TokenType     TokenType   `json:"token_type,omitempty"`     // Type of tokens used in the request
+	CombineText   string      `json:"combine_text,omitempty"`   // Combined text from all messages
+	ToolsCount    int         `json:"tools_count,omitempty"`    // Number of tools used
+	NameCount     int         `json:"name_count,omitempty"`     // Number of names in the request
+	MessagesCount int         `json:"messages_count,omitempty"` // Number of messages in the request
+	Files         []*FileMeta `json:"files,omitempty"`          // List of files, each with type and content
+	MaxTokens     int         `json:"max_tokens,omitempty"`     // Maximum tokens allowed in the request
+
+	ImagePriceRatio float64 `json:"image_ratio,omitempty"` // Ratio for image size, if applicable
+	//IsStreaming   bool        `json:"is_streaming,omitempty"`   // Indicates if the request is streaming
+}
+
+type FileMeta struct {
+	FileType
+	MimeType string
+	Data     string
+	Detail   string
+}
+
+type RequestMeta struct {
+	OriginalModelName string `json:"original_model_name"`
+	UserUsingGroup    string `json:"user_using_group"`
+	PromptTokens      int    `json:"prompt_tokens"`
+	PreConsumedQuota  int    `json:"pre_consumed_quota"`
+}