🚚 Refactor(ratio_setting): refactor ratio management into standalone ratio_setting package

Summary
• Migrated all ratio-related sources into `setting/ratio_setting/`
  – `model_ratio.go` (renamed from model-ratio.go)
  – `cache_ratio.go`
  – `group_ratio.go`
• Changed package name to `ratio_setting` and relocated initialization (`ratio_setting.InitRatioSettings()` in main).
• Updated every import & call site:
  – Model / cache / completion / image ratio helpers
  – Group ratio helpers (`GetGroupRatio*`, `ContainsGroupRatio`, `CheckGroupRatio`, etc.)
  – JSON-serialization & update helpers (`*Ratio2JSONString`, `Update*RatioByJSONString`)
• Adjusted controllers, middleware, relay helpers, services and models to reference the new package.
• Removed obsolete `setting` / `operation_setting` imports; added missing `ratio_setting` imports.
• Adopted idiomatic map iteration (`for key := range m`) where value is unused.
• Ran static checks to ensure clean build.

This commit centralises all ratio configuration (model, cache and group) in one cohesive module, simplifying future maintenance and improving code clarity.

setting/ratio_setting/cache_ratio.go

@@ -1,4 +1,4 @@
-package operation_setting
+package ratio_setting
 
 import (
 	"encoding/json"

setting/ratio_setting/group_ratio.go

@@ -1,4 +1,4 @@
-package setting
+package ratio_setting
 
 import (
 	"encoding/json"

setting/ratio_setting/model_ratio.go

@@ -1,8 +1,9 @@
-package operation_setting
+package ratio_setting
 
 import (
 	"encoding/json"
 	"one-api/common"
+	"one-api/setting/operation_setting"
 	"strings"
 	"sync"
 )
@@ -366,7 +367,7 @@ func GetModelRatio(name string) (float64, bool) {
 	}
 	ratio, ok := modelRatioMap[name]
 	if !ok {
-		return 37.5, SelfUseModeEnabled
+		return 37.5, operation_setting.SelfUseModeEnabled
 	}
 	return ratio, true
 }