refactor(edge): 抽取边缘运行时共享包并完成 Phase 3 重构

- 新增 internal/apps/edge/，三组件改为薄包装，删除 3000+ 行重复代码
- Agent 心跳周期下沉至 heartbeat/cycle.go
- 协议类型迁入 pkg/protocol/agent.go
- 补充设计文档与 changelog

internal/apps/flared/httpclient/client.go

@@ -1,16 +1,10 @@
 package httpclient
 
 import (
-	"bytes"
 	"context"
-	"encoding/json"
-	"errors"
-	"io"
-	"log/slog"
-	"net/http"
-	"strings"
 	"time"
 
+	edgehttp "github.com/Rain-kl/Wavelet/internal/apps/edge/httpclient"
 	service "github.com/Rain-kl/Wavelet/pkg/protocol"
 )
 
@@ -20,27 +14,21 @@ type APIResponse[T any] struct {
 }
 
 type Client struct {
-	baseURL    string
-	token      string
-	httpClient *http.Client
+	base *edgehttp.Client
 }
 
 func New(baseURL string, token string, timeout time.Duration) *Client {
 	return &Client{
-		baseURL: strings.TrimRight(baseURL, "/"),
-		token:   token,
-		httpClient: &http.Client{
-			Timeout: timeout,
-		},
+		base: edgehttp.New(baseURL, token, timeout, "X-Tunnel-Token"),
 	}
 }
 
 func (c *Client) Heartbeat(ctx context.Context, payload service.FlaredHeartbeatPayload) (*service.FlaredHeartbeatResponse, error) {
 	resp := APIResponse[service.FlaredHeartbeatResponse]{}
-	if err := c.postJSON(ctx, "/api/v1/tunnel/heartbeat", payload, &resp); err != nil {
+	if err := c.base.PostJSON(ctx, "/api/v1/tunnel/heartbeat", payload, &resp); err != nil {
 		return nil, err
 	}
-	if err := apiError(resp.ErrorMsg); err != nil {
+	if err := edgehttp.APIError(resp.ErrorMsg); err != nil {
 		return nil, err
 	}
 	return &resp.Data, nil
@@ -48,10 +36,10 @@ func (c *Client) Heartbeat(ctx context.Context, payload service.FlaredHeartbeatP
 
 func (c *Client) GetActiveConfig(ctx context.Context) (*service.FlaredTunnelConfigResponse, error) {
 	resp := APIResponse[service.FlaredTunnelConfigResponse]{}
-	if err := c.getJSON(ctx, "/api/v1/tunnel/config/active", &resp); err != nil {
+	if err := c.base.GetJSON(ctx, "/api/v1/tunnel/config/active", &resp); err != nil {
 		return nil, err
 	}
-	if err := apiError(resp.ErrorMsg); err != nil {
+	if err := edgehttp.APIError(resp.ErrorMsg); err != nil {
 		return nil, err
 	}
 	return &resp.Data, nil
@@ -59,85 +47,12 @@ func (c *Client) GetActiveConfig(ctx context.Context) (*service.FlaredTunnelConf
 
 func (c *Client) ReportApplyLog(ctx context.Context, payload service.ApplyLogPayload) error {
 	resp := APIResponse[any]{}
-	if err := c.postJSON(ctx, "/api/v1/tunnel/apply-log", payload, &resp); err != nil {
+	if err := c.base.PostJSON(ctx, "/api/v1/tunnel/apply-log", payload, &resp); err != nil {
 		return err
 	}
-	return apiError(resp.ErrorMsg)
+	return edgehttp.APIError(resp.ErrorMsg)
 }
 
 func (c *Client) SetToken(token string) {
-	c.token = strings.TrimSpace(token)
-	slog.Debug("http client token updated")
-}
-
-func (c *Client) getJSON(ctx context.Context, path string, target any) error {
-	req, err := http.NewRequestWithContext(ctx, http.MethodGet, c.baseURL+path, nil)
-	if err != nil {
-		return err
-	}
-	req.Header.Set("X-Tunnel-Token", c.token)
-	return c.do(req, target)
-}
-
-func (c *Client) postJSON(ctx context.Context, path string, body any, target any) error {
-	data, err := json.Marshal(body)
-	if err != nil {
-		return err
-	}
-	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+path, bytes.NewReader(data))
-	if err != nil {
-		return err
-	}
-	req.Header.Set("Content-Type", "application/json")
-	req.Header.Set("X-Tunnel-Token", c.token)
-	return c.do(req, target)
-}
-
-func (c *Client) do(req *http.Request, target any) error {
-	res, err := c.httpClient.Do(req)
-	if err != nil {
-		slog.Error("http request failed", "method", req.Method, "path", req.URL.Path, "error", err)
-		return err
-	}
-	defer func(Body io.ReadCloser) {
-		err := Body.Close()
-		if err != nil {
-			slog.Error("failed to close response body", "error", err)
-		}
-	}(res.Body)
-
-	body, err := io.ReadAll(res.Body)
-	if err != nil {
-		slog.Error("http response read failed", "method", req.Method, "path", req.URL.Path, "error", err)
-		return err
-	}
-	if res.StatusCode != http.StatusOK {
-		slog.Warn("http request returned non-200", "method", req.Method, "path", req.URL.Path, "status", res.Status)
-		return readBodyError(body, res.Status)
-	}
-	if target == nil {
-		return nil
-	}
-	if err = json.Unmarshal(body, target); err != nil {
-		slog.Error("http response decode failed", "method", req.Method, "path", req.URL.Path, "error", err)
-		return err
-	}
-	return nil
-}
-
-func apiError(msg string) error {
-	if strings.TrimSpace(msg) == "" {
-		return nil
-	}
-	return errors.New(msg)
-}
-
-func readBodyError(body []byte, fallback string) error {
-	var errBody struct {
-		ErrorMsg string `json:"error_msg"`
-	}
-	if err := json.Unmarshal(body, &errBody); err == nil && strings.TrimSpace(errBody.ErrorMsg) != "" {
-		return errors.New(errBody.ErrorMsg)
-	}
-	return errors.New(fallback)
-}
+	c.base.SetToken(token)
+}