feat(server): meter AI point usage across tenant AI features

Adds an ai_point_usage_logs ledger and a reserve/refund/complete pipeline
that charges AI points for article selection optimize, template analyze
/title/outline, and KOL prompt generate/optimize. Pending reservations
are reconciled when the kol-assist worker and template-assist tasks
finish or fail, so points refund automatically on errors. Workspace now
exposes the AI quota status and a paginated usage ledger.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/internal/tenant/repository/quota_repo.go

@@ -19,6 +19,16 @@ type ArticleQuotaStatus struct {
 	ResetAt  *time.Time
 }
 
+type AIQuotaStatus struct {
+	PlanCode  string
+	PlanName  string
+	Total     int
+	Used      int
+	Balance   int
+	BaseChars int
+	ResetAt   *time.Time
+}
+
 type QuotaLedgerInput struct {
 	TenantID      int64
 	OperatorID    int64
@@ -43,6 +53,7 @@ type QuotaReservationInput struct {
 type QuotaRepository interface {
 	GetCurrentBalance(ctx context.Context, tenantID int64, quotaType string) (int, error)
 	GetArticleQuotaStatus(ctx context.Context, tenantID int64, now time.Time) (*ArticleQuotaStatus, error)
+	GetAIQuotaStatus(ctx context.Context, tenantID int64, now time.Time) (*AIQuotaStatus, error)
 	InsertQuotaLedger(ctx context.Context, input QuotaLedgerInput) (int64, error)
 	CreateQuotaReservation(ctx context.Context, input QuotaReservationInput) (int64, error)
 	UpdateQuotaReservationResource(ctx context.Context, reservationID, tenantID, resourceID int64) error
@@ -78,6 +89,58 @@ func (r *quotaRepository) GetCurrentBalance(ctx context.Context, tenantID int64,
 	return status.Balance, nil
 }
 
+func (r *quotaRepository) GetAIQuotaStatus(ctx context.Context, tenantID int64, now time.Time) (*AIQuotaStatus, error) {
+	access, err := loadTenantPlanAccess(ctx, r.db, tenantID, now)
+	if err != nil {
+		return nil, err
+	}
+	if access == nil {
+		return nil, pgx.ErrNoRows
+	}
+
+	baseChars := access.AIPointBaseChars()
+	if !access.HasActiveAccess(now) {
+		return &AIQuotaStatus{
+			PlanCode:  access.PlanCode,
+			PlanName:  access.PlanName,
+			BaseChars: baseChars,
+		}, nil
+	}
+
+	total := access.AIPointsMonthlyLimit()
+	if total <= 0 {
+		return &AIQuotaStatus{
+			PlanCode:  access.PlanCode,
+			PlanName:  access.PlanName,
+			BaseChars: baseChars,
+		}, nil
+	}
+
+	windowStart, windowEnd, resetAt := access.AIPointsWindow(now)
+	if windowEnd.IsZero() {
+		return nil, errors.New("ai points quota window end is missing")
+	}
+
+	used, err := CountEffectiveQuotaReservations(ctx, r.db, tenantID, "ai_points", windowStart, windowEnd)
+	if err != nil {
+		return nil, err
+	}
+	balance := total - used
+	if balance < 0 {
+		balance = 0
+	}
+
+	return &AIQuotaStatus{
+		PlanCode:  access.PlanCode,
+		PlanName:  access.PlanName,
+		Total:     total,
+		Used:      used,
+		Balance:   balance,
+		BaseChars: baseChars,
+		ResetAt:   resetAt,
+	}, nil
+}
+
 func (r *quotaRepository) GetArticleQuotaStatus(ctx context.Context, tenantID int64, now time.Time) (*ArticleQuotaStatus, error) {
 	access, err := loadTenantPlanAccess(ctx, r.db, tenantID, now)
 	if err != nil {