feat(server/membership): add ai_points plan policy fields

Introduces ai_points_monthly and ai_point_base_chars on the membership
plan policy, exposes them through TenantPlanAccess and MembershipInfo,
and seeds Pro with a 1500-point monthly allowance across the local,
server, and deploy configs.

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

server/internal/tenant/repository/tenant_plan_repo.go

@@ -98,6 +98,38 @@ func (a *TenantPlanAccess) ArticleQuotaCycle() string {
 	}
 }
 
+func (a *TenantPlanAccess) AIPointsMonthlyLimit() int {
+	if a == nil {
+		return 0
+	}
+	return maxInt(a.Policy.AIPointsMonthly, 0)
+}
+
+func (a *TenantPlanAccess) AIPointBaseChars() int {
+	if a == nil || a.Policy.AIPointBaseChars <= 0 {
+		return 1000
+	}
+	return a.Policy.AIPointBaseChars
+}
+
+func (a *TenantPlanAccess) AIPointsWindow(now time.Time) (time.Time, time.Time, *time.Time) {
+	if a == nil {
+		return time.Time{}, time.Time{}, nil
+	}
+
+	windowStart := a.StartAt.UTC()
+	windowEnd := a.EndAt.UTC()
+	cycleStart, cycleEnd := monthlyCycleBounds(windowStart, now.UTC())
+	if cycleStart.Before(windowStart) {
+		cycleStart = windowStart
+	}
+	if !windowEnd.IsZero() && cycleEnd.After(windowEnd) {
+		cycleEnd = windowEnd
+	}
+	resetAt := cycleEnd
+	return cycleStart, cycleEnd, &resetAt
+}
+
 func (a *TenantPlanAccess) ArticleQuotaWindow(now time.Time) (time.Time, time.Time, *time.Time) {
 	if a == nil {
 		return time.Time{}, time.Time{}, nil