Integrate Qiniu upload service and update configuration

- Added Qiniu configuration options to .env.example and config.go for file uploads.
- Refactored main.go to include new Qiniu service and upload handler.
- Updated route registration to accommodate the new upload handler.
- Enhanced documentation to include references for Qiniu upload functionality.
- Removed legacy authentication handler and services to streamline the codebase.

internal/common/auth/service/wechat_client.go

@@ -0,0 +1,89 @@
+package service
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/url"
+	"time"
+)
+
+const weChatCode2SessionURL = "https://api.weixin.qq.com/sns/jscode2session"
+
+// WeChatClient 调用微信接口获取 session/openid。
+type WeChatClient struct {
+	appID     string
+	appSecret string
+	client    *http.Client
+}
+
+type WeChatSession struct {
+	OpenID     string `json:"openid"`
+	UnionID    string `json:"unionid"`
+	SessionKey string `json:"session_key"`
+}
+
+type weChatSessionResponse struct {
+	WeChatSession
+	ErrCode int    `json:"errcode"`
+	ErrMsg  string `json:"errmsg"`
+}
+
+// WeChatError 表示微信接口级错误。
+type WeChatError struct {
+	Code int
+	Msg  string
+}
+
+func (e *WeChatError) Error() string {
+	return fmt.Sprintf("wechat error: code=%d msg=%s", e.Code, e.Msg)
+}
+
+func NewWeChatClient(appID, appSecret string, client *http.Client) *WeChatClient {
+	if client == nil {
+		client = &http.Client{
+			Timeout: 5 * time.Second,
+		}
+	}
+
+	return &WeChatClient{
+		appID:     appID,
+		appSecret: appSecret,
+		client:    client,
+	}
+}
+
+func (c *WeChatClient) Code2Session(ctx context.Context, code string) (*WeChatSession, error) {
+	query := url.Values{}
+	query.Set("appid", c.appID)
+	query.Set("secret", c.appSecret)
+	query.Set("js_code", code)
+	query.Set("grant_type", "authorization_code")
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, fmt.Sprintf("%s?%s", weChatCode2SessionURL, query.Encode()), nil)
+	if err != nil {
+		return nil, fmt.Errorf("build wechat request: %w", err)
+	}
+
+	resp, err := c.client.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("call wechat api: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("wechat api unexpected status: %s", resp.Status)
+	}
+
+	var raw weChatSessionResponse
+	if err := json.NewDecoder(resp.Body).Decode(&raw); err != nil {
+		return nil, fmt.Errorf("decode wechat response: %w", err)
+	}
+
+	if raw.ErrCode != 0 {
+		return nil, &WeChatError{Code: raw.ErrCode, Msg: raw.ErrMsg}
+	}
+
+	return &raw.WeChatSession, nil
+}