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.

dto/embedding.go

@@ -1,5 +1,12 @@
 package dto
 
+import (
+	"one-api/types"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+)
+
 type EmbeddingOptions struct {
 	Seed             int      `json:"seed,omitempty"`
 	Temperature      *float64 `json:"temperature,omitempty"`
@@ -24,9 +31,26 @@ type EmbeddingRequest struct {
 	PresencePenalty  float64  `json:"presence_penalty,omitempty"`
 }
 
-func (r EmbeddingRequest) ParseInput() []string {
+func (r *EmbeddingRequest) GetTokenCountMeta() *types.TokenCountMeta {
+	var texts = make([]string, 0)
+
+	inputs := r.ParseInput()
+	for _, input := range inputs {
+		texts = append(texts, input)
+	}
+
+	return &types.TokenCountMeta{
+		CombineText: strings.Join(texts, "\n"),
+	}
+}
+
+func (r *EmbeddingRequest) IsStream(c *gin.Context) bool {
+	return false
+}
+
+func (r *EmbeddingRequest) ParseInput() []string {
 	if r.Input == nil {
-		return nil
+		return make([]string, 0)
 	}
 	var input []string
 	switch r.Input.(type) {