refactor(api): standardize DTOs and update swagger

Decouple API contract from internal models by introducing dedicated DTOs for requests and responses.
- Add Response DTOs for all resources (API Keys, Bindings, Models, Namespaces, etc.)
- Update Swagger annotations to use DTOs with field examples instead of internal models
- Refactor handlers to bind and return DTO structures
- Consolidate request/response definitions in the dto package

internal/dto/log_record.go

@@ -0,0 +1,24 @@
+package dto
+
+// LogRecordRequest defines the request body for log ingestion.
+// @Description Log record ingest request
+type LogRecordRequest struct {
+	Group        string `json:"group" example:"default"`
+	MasterID     uint   `json:"master_id" example:"1"`
+	KeyID        uint   `json:"key_id" example:"1"`
+	ModelName    string `json:"model" example:"gpt-4"`
+	ProviderID   uint   `json:"provider_id" example:"1"`
+	ProviderType string `json:"provider_type" example:"openai"`
+	ProviderName string `json:"provider_name" example:"openai-prod"`
+	StatusCode   int    `json:"status_code" example:"200"`
+	LatencyMs    int64  `json:"latency_ms" example:"150"`
+	TokensIn     int64  `json:"tokens_in" example:"100"`
+	TokensOut    int64  `json:"tokens_out" example:"50"`
+	ErrorMessage string `json:"error_message,omitempty"`
+	ClientIP     string `json:"client_ip" example:"192.168.1.1"`
+	RequestSize  int64  `json:"request_size" example:"1024"`
+	ResponseSize int64  `json:"response_size" example:"2048"`
+	AuditReason  string `json:"audit_reason,omitempty"`
+	RequestBody  string `json:"request_body,omitempty"`
+	ResponseBody string `json:"response_body,omitempty"`
+}