feat: Add Swagger documentation for admin and master API endpoints

- Added Swagger documentation for the following admin endpoints:
  - Create a new master tenant
  - Create a new provider
  - Register a new model
  - List all models
  - Update a model
  - Force sync snapshot
  - Ingest logs

- Added Swagger documentation for the master endpoint:
  - Issue a child key

- Updated go.mod and go.sum to include necessary dependencies for Swagger.

internal/api/master_handler.go

@@ -23,6 +23,20 @@ type IssueChildKeyRequest struct {
 	Scopes string `json:"scopes"`
 }
 
+// IssueChildKey godoc
+// @Summary      Issue a child key
+// @Description  Issue a new access token (child key) for the authenticated master
+// @Tags         master
+// @Accept       json
+// @Produce      json
+// @Security     MasterAuth
+// @Param        request  body      IssueChildKeyRequest  true  "Key Request"
+// @Success      201      {object}  gin.H
+// @Failure      400      {object}  gin.H
+// @Failure      401      {object}  gin.H
+// @Failure      403      {object}  gin.H
+// @Failure      500      {object}  gin.H
+// @Router       /v1/tokens [post]
 func (h *MasterHandler) IssueChildKey(c *gin.Context) {
 	master, exists := c.Get("master")
 	if !exists {