refactor(service): remove legacy routing and unused code

Removes the legacy route table maintenance logic from the sync service
that populated deprecated Redis keys. Additionally, deletes the unused
TokenService and KeyDTO files to reduce technical debt.

internal/dto/key.go

@@ -1,10 +0,0 @@
-package dto
-
-// KeyDTO defines payload for key creation/update.
-type KeyDTO struct {
-	Group     string  `json:"group"`
-	KeySecret string  `json:"key_secret"`
-	Balance   float64 `json:"balance"`
-	Status    string  `json:"status"`
-	Weight    int     `json:"weight"`
-}