fix: 修复keys速率限制未自动重置额度的bug

backend/internal/service/api_key.go

@@ -14,6 +14,18 @@ const (
 	StatusAPIKeyExpired        = "expired"
 )
 
+// Rate limit window durations
+const (
+	RateLimitWindow5h = 5 * time.Hour
+	RateLimitWindow1d = 24 * time.Hour
+	RateLimitWindow7d = 7 * 24 * time.Hour
+)
+
+// IsWindowExpired returns true if the window starting at windowStart has exceeded the given duration.
+func IsWindowExpired(windowStart *time.Time, duration time.Duration) bool {
+	return windowStart != nil && time.Since(*windowStart) >= duration
+}
+
 type APIKey struct {
 	ID          int64
 	UserID      int64
@@ -98,6 +110,30 @@ func (k *APIKey) GetDaysUntilExpiry() int {
 	return int(duration.Hours() / 24)
 }
 
+// EffectiveUsage5h returns the 5h window usage, or 0 if the window has expired.
+func (k *APIKey) EffectiveUsage5h() float64 {
+	if IsWindowExpired(k.Window5hStart, RateLimitWindow5h) {
+		return 0
+	}
+	return k.Usage5h
+}
+
+// EffectiveUsage1d returns the 1d window usage, or 0 if the window has expired.
+func (k *APIKey) EffectiveUsage1d() float64 {
+	if IsWindowExpired(k.Window1dStart, RateLimitWindow1d) {
+		return 0
+	}
+	return k.Usage1d
+}
+
+// EffectiveUsage7d returns the 7d window usage, or 0 if the window has expired.
+func (k *APIKey) EffectiveUsage7d() float64 {
+	if IsWindowExpired(k.Window7dStart, RateLimitWindow7d) {
+		return 0
+	}
+	return k.Usage7d
+}
+
 // APIKeyListFilters holds optional filtering parameters for listing API keys.
 type APIKeyListFilters struct {
 	Search  string