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/price_data.go

@@ -0,0 +1,31 @@
+package types
+
+import "fmt"
+
+type GroupRatioInfo struct {
+	GroupRatio        float64
+	GroupSpecialRatio float64
+	HasSpecialRatio   bool
+}
+
+type PriceData struct {
+	ModelPrice             float64
+	ModelRatio             float64
+	CompletionRatio        float64
+	CacheRatio             float64
+	CacheCreationRatio     float64
+	ImageRatio             float64
+	UsePrice               bool
+	ShouldPreConsumedQuota int
+	GroupRatioInfo         GroupRatioInfo
+}
+
+type PerCallPriceData struct {
+	ModelPrice     float64
+	Quota          int
+	GroupRatioInfo GroupRatioInfo
+}
+
+func (p PriceData) ToSetting() string {
+	return fmt.Sprintf("ModelPrice: %f, ModelRatio: %f, CompletionRatio: %f, CacheRatio: %f, GroupRatio: %f, UsePrice: %t, CacheCreationRatio: %f, ShouldPreConsumedQuota: %d, ImageRatio: %f", p.ModelPrice, p.ModelRatio, p.CompletionRatio, p.CacheRatio, p.GroupRatioInfo.GroupRatio, p.UsePrice, p.CacheCreationRatio, p.ShouldPreConsumedQuota, p.ImageRatio)
+}