chore: 初始化 eightbf-analysis-go（对齐 Java 会商作业服务）

Go 实现 /api/v1/analysis 契约、Demo/Live Worker、DeerFlow SSE；含设计文档与冒烟脚本。

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/deerflow/auth.go

@@ -0,0 +1,72 @@
+package deerflow
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"sync"
+	"time"
+
+	"git.gozeros.com/wsk/eightbf-analysis-go/internal/config"
+)
+
+// Auth 向 DeerFlow 换 Bearer，过期前复用。
+type Auth struct {
+	cfg        config.Config
+	mu         sync.Mutex
+	token      string
+	expiresAt  time.Time
+	httpClient *http.Client
+}
+
+func NewAuth(cfg config.Config) *Auth {
+	return &Auth{
+		cfg:        cfg,
+		httpClient: &http.Client{Timeout: 30 * time.Second},
+	}
+}
+
+func (a *Auth) BearerToken() (string, error) {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	now := time.Now()
+	if a.token != "" && a.expiresAt.After(now.Add(2*time.Minute)) {
+		return a.token, nil
+	}
+	body, _ := json.Marshal(map[string]string{
+		"username": a.cfg.DeerFlowUser,
+		"password": a.cfg.DeerFlowPassword,
+	})
+	req, err := http.NewRequest(http.MethodPost, a.cfg.DeerFlowBaseURL+"/api/v1/auth/login/username", bytes.NewReader(body))
+	if err != nil {
+		return "", err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	resp, err := a.httpClient.Do(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+	raw, _ := io.ReadAll(resp.Body)
+	if resp.StatusCode >= 400 {
+		return "", fmt.Errorf("DeerFlow 登录失败 HTTP %d: %s", resp.StatusCode, string(raw))
+	}
+	var parsed struct {
+		AccessToken string `json:"access_token"`
+		ExpiresIn   int    `json:"expires_in"`
+	}
+	if err := json.Unmarshal(raw, &parsed); err != nil {
+		return "", err
+	}
+	if parsed.AccessToken == "" {
+		return "", fmt.Errorf("DeerFlow 登录响应无 access_token")
+	}
+	if parsed.ExpiresIn <= 0 {
+		parsed.ExpiresIn = 3600
+	}
+	a.token = parsed.AccessToken
+	a.expiresAt = now.Add(time.Duration(parsed.ExpiresIn) * time.Second)
+	return a.token, nil
+}