refactor: move backend files to backend/ directory

Reorganize project structure:
- backend/cmd/openteam/ — entry point
- backend/internal/ — core packages
- backend/middleware/ — HTTP middleware
- backend/router/ — route setup
- backend/wire/ — dependency injection
- backend/pkg/ — shared utilities
- backend/go.mod, go.sum — Go module files

Updated Makefile to work from backend/ directory.
Removed old lowercase makefile.

backend/middleware/auth.go

@@ -0,0 +1,53 @@
+package middleware
+
+import (
+	"net/http"
+	"opencatd-open/internal/auth"
+	"opencatd-open/internal/store"
+	"opencatd-open/internal/pkg/jwt"
+
+	"github.com/gin-gonic/gin"
+	"gorm.io/gorm"
+)
+
+func Auth(db *gorm.DB) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		authToken := c.GetHeader("Authorization")
+		if authToken == "" {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
+				"code":  http.StatusUnauthorized,
+				"error": "未提供认证信息",
+			})
+			return
+		}
+		if len(authToken) > 7 {
+			authToken = authToken[7:]
+		}
+		claim, err := jwt.ValidateToken(authToken, auth.GetSecretKey())
+		if err != nil {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
+				"code":  http.StatusUnauthorized,
+				"error": "无效的认证信息",
+			})
+			return
+		}
+		var user store.User
+		if err := db.First(&user, claim.UserID).Error; err != nil {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
+				"code":  http.StatusUnauthorized,
+				"error": "无效的认证信息",
+			})
+			return
+		}
+		c.Set("user", &user)
+		c.Set("user_id", claim.UserID)
+		c.Set("user_role", user.Role)
+		c.Next()
+	}
+}
+
+func CheckRole(role string) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		c.Next()
+	}
+}

backend/middleware/auth_llm.go

@@ -0,0 +1,67 @@
+package middleware
+
+import (
+	"net/http"
+	"opencatd-open/internal/store"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+	"gorm.io/gorm"
+)
+
+func AuthLLM(db *gorm.DB) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		authToken := c.GetHeader("Authorization")
+		if authToken == "" {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
+				"error": map[string]interface{}{
+					"message": "未提供认证信息",
+					"type":    "invalid_request_error",
+				},
+			})
+			return
+		}
+
+		// Extract API key from Bearer token
+		if len(authToken) > 7 {
+			authToken = authToken[7:]
+		}
+
+		// Find API key by prefix
+		var apiKey store.APIKey
+		if err := db.Where("key_prefix = ? AND status = ?", authToken[:8], store.KeyStatusActive).First(&apiKey).Error; err != nil {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
+				"error": map[string]interface{}{
+					"message": "无效的API密钥",
+					"type":    "invalid_request_error",
+				},
+			})
+			return
+		}
+
+		// Verify full key hash
+		keyHash := store.HashAPIKey(authToken)
+		if apiKey.KeyHash != keyHash {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
+				"error": map[string]interface{}{
+					"message": "无效的API密钥",
+					"type":    "invalid_request_error",
+				},
+			})
+			return
+		}
+
+		c.Set("api_key", &apiKey)
+		c.Set("user_id", apiKey.UserID)
+		c.Next()
+	}
+}
+
+// extractAPIKey extracts the API key from the Authorization header
+func extractAPIKey(c *gin.Context) string {
+	auth := c.GetHeader("Authorization")
+	if strings.HasPrefix(auth, "Bearer ") {
+		return auth[7:]
+	}
+	return auth
+}

backend/middleware/cors.go

@@ -0,0 +1,15 @@
+package middleware
+
+import (
+	"github.com/gin-contrib/cors"
+	"github.com/gin-gonic/gin"
+)
+
+func CORS() gin.HandlerFunc {
+	config := cors.DefaultConfig()
+	config.AllowAllOrigins = true
+	config.AllowCredentials = true
+	config.AllowMethods = []string{"GET", "POST", "PUT", "DELETE", "OPTIONS"}
+	config.AllowHeaders = []string{"*"}
+	return cors.New(config)
+}

backend/middleware/ratelimit.go

@@ -0,0 +1,53 @@
+package middleware
+
+import (
+	"net/http"
+	"sync"
+
+	"github.com/gin-gonic/gin"
+	"golang.org/x/time/rate"
+)
+
+type IPRateLimiter struct {
+	ips map[string]*rate.Limiter
+	mu  *sync.RWMutex
+	r   rate.Limit
+	b   int
+}
+
+func NewIPRateLimiter(r rate.Limit, b int) *IPRateLimiter {
+	return &IPRateLimiter{
+		ips: make(map[string]*rate.Limiter),
+		mu:  &sync.RWMutex{},
+		r:   r,
+		b:   b,
+	}
+}
+
+func (i *IPRateLimiter) GetLimiter(ip string) *rate.Limiter {
+	i.mu.Lock()
+	defer i.mu.Unlock()
+
+	limiter, exists := i.ips[ip]
+	if !exists {
+		limiter = rate.NewLimiter(i.r, i.b)
+		i.ips[ip] = limiter
+	}
+
+	return limiter
+}
+
+func RateLimit(limiter *IPRateLimiter) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		ip := c.ClientIP()
+		if !limiter.GetLimiter(ip).Allow() {
+			c.JSON(http.StatusTooManyRequests, gin.H{
+				"code":    429,
+				"message": "too many requests",
+			})
+			c.Abort()
+			return
+		}
+		c.Next()
+	}
+}