refactor(api): restructured API for type safety, maintainability and docs generation

- These changes makes the API incombatible with previous versions
- Added new types for error handling, success responses, and health checks.
- Updated health check logic to utilize the new types for better clarity and structure.
- Refactored existing handlers to improve response consistency and error handling.
- Updated Makefile to include a new target for generating API types from Swagger.
- Updated "new agent" API to respond an encrypted cert pair

internal/api/v1/agent/list.go

@@ -0,0 +1,32 @@
+package agentapi
+
+import (
+	"net/http"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/yusing/go-proxy/agent/pkg/agent"
+	"github.com/yusing/go-proxy/internal/net/gphttp/httpheaders"
+	"github.com/yusing/go-proxy/internal/net/gphttp/websocket"
+)
+
+// @x-id				"list"
+// @BasePath		/api/v1
+// @Summary		List agents
+// @Description	List agents
+// @Tags			agent,websocket
+// @Accept			json
+// @Produce		json
+// @Success		200	{array}		Agent
+// @Failure		403	{object}	apitypes.ErrorResponse
+// @Failure		500	{object}	apitypes.ErrorResponse
+// @Router			/agent/list [get]
+func List(c *gin.Context) {
+	if httpheaders.IsWebsocket(c.Request.Header) {
+		websocket.PeriodicWrite(c, 10*time.Second, func() (any, error) {
+			return agent.ListAgents(), nil
+		})
+	} else {
+		c.JSON(http.StatusOK, agent.ListAgents())
+	}
+}