feat: design system overhaul — sidebar, AI chats, settings, brainstorm, color cleanup

- Sidebar: dynamic brand-accent colors, brainstorm section restyled
- AI chat general: popup panel with expand/collapse, hides when contextual AI open
- AI chat contextual: tabs reordered (Actions first), X close button, height fix
- Settings: all tabs restyled, 6 new color presets (sage, terracotta, iron, etc.)
- Global color cleanup: emerald/orange hardcoded → brand-accent dynamic
- Brainstorm page: orange → brand-accent throughout
- PageEntry animation component added to key pages
- Floating AI button: bg-brand-accent instead of hardcoded black
- i18n: all 15 locales updated with new AI/billing keys
- Billing: freemium quota tracking, BYOK, stripe subscription scaffolding
- Admin: integrated into new design
- AGENTS.md + CLAUDE.md project rules added

memento-note/lib/billing/stripe-prices.ts

@@ -0,0 +1,35 @@
+import type { SubscriptionTier } from '@/lib/entitlements';
+
+export type BillingTier = 'PRO' | 'BUSINESS';
+export type BillingInterval = 'month' | 'year';
+
+export function resolvePriceId(tier: BillingTier, interval: BillingInterval): string {
+  const map: Record<BillingTier, Record<BillingInterval, string>> = {
+    PRO: {
+      month: process.env.STRIPE_PRICE_PRO_MONTHLY!,
+      year: process.env.STRIPE_PRICE_PRO_ANNUAL!,
+    },
+    BUSINESS: {
+      month: process.env.STRIPE_PRICE_BUSINESS_MONTHLY!,
+      year: process.env.STRIPE_PRICE_BUSINESS_ANNUAL!,
+    },
+  };
+  const priceId = map[tier][interval];
+  if (!priceId) {
+    throw new Error(`No Stripe price ID configured for ${tier}/${interval}`);
+  }
+  return priceId;
+}
+
+export function priceIdToTier(priceId: string): SubscriptionTier | null {
+  const entries: Array<[string | undefined, SubscriptionTier]> = [
+    [process.env.STRIPE_PRICE_PRO_MONTHLY, 'PRO'],
+    [process.env.STRIPE_PRICE_PRO_ANNUAL, 'PRO'],
+    [process.env.STRIPE_PRICE_BUSINESS_MONTHLY, 'BUSINESS'],
+    [process.env.STRIPE_PRICE_BUSINESS_ANNUAL, 'BUSINESS'],
+  ];
+  for (const [envPriceId, tier] of entries) {
+    if (envPriceId && envPriceId === priceId) return tier;
+  }
+  return null;
+}

memento-note/lib/billing/sync-subscription-from-stripe.ts

@@ -0,0 +1,113 @@
+import type Stripe from 'stripe';
+import { prisma } from '@/lib/prisma';
+import { priceIdToTier } from '@/lib/billing/stripe-prices';
+import { SubscriptionStatus, SubscriptionTier } from '@prisma/client';
+
+function mapStripeStatus(stripeStatus: Stripe.Subscription.Status): SubscriptionStatus {
+  switch (stripeStatus) {
+    case 'active':
+      return SubscriptionStatus.ACTIVE;
+    case 'trialing':
+      return SubscriptionStatus.TRIALING;
+    case 'past_due':
+      return SubscriptionStatus.PAST_DUE;
+    case 'canceled':
+    case 'unpaid':
+      return SubscriptionStatus.CANCELED;
+    case 'incomplete':
+    case 'incomplete_expired':
+      return SubscriptionStatus.INACTIVE;
+    default:
+      return SubscriptionStatus.INACTIVE;
+  }
+}
+
+export async function syncSubscriptionFromStripe(
+  subscription: Stripe.Subscription,
+  userId: string,
+): Promise<void> {
+  const priceId = subscription.items.data[0]?.price?.id ?? null;
+  const resolvedTier = priceId ? priceIdToTier(priceId) : null;
+
+  const tierFromMetadata =
+    (subscription.metadata?.tier as string | undefined) ??
+    (subscription.metadata?.tier as string | undefined);
+
+  let tier: SubscriptionTier;
+  if (resolvedTier) {
+    tier = resolvedTier as SubscriptionTier;
+  } else if (tierFromMetadata === 'PRO' || tierFromMetadata === 'BUSINESS' || tierFromMetadata === 'ENTERPRISE') {
+    tier = tierFromMetadata as SubscriptionTier;
+  } else {
+    tier = SubscriptionTier.BASIC;
+  }
+
+  const status = mapStripeStatus(subscription.status);
+
+  const currentPeriodStart = new Date(((subscription as any).current_period_start as number) * 1000);
+  const currentPeriodEnd = new Date(((subscription as any).current_period_end as number) * 1000);
+
+  await prisma.subscription.upsert({
+    where: { stripeSubscriptionId: subscription.id },
+    update: {
+      tier,
+      status,
+      stripeCustomerId: typeof subscription.customer === 'string' ? subscription.customer : subscription.customer.id,
+      stripePriceId: priceId,
+      currentPeriodStart,
+      currentPeriodEnd,
+      cancelAtPeriodEnd: subscription.cancel_at_period_end,
+      canceledAt: subscription.canceled_at ? new Date(subscription.canceled_at * 1000) : null,
+      trialEndsAt: subscription.trial_end ? new Date(subscription.trial_end * 1000) : null,
+      updatedAt: new Date(),
+    },
+    create: {
+      userId,
+      tier,
+      status,
+      stripeCustomerId: typeof subscription.customer === 'string' ? subscription.customer : subscription.customer.id,
+      stripeSubscriptionId: subscription.id,
+      stripePriceId: priceId,
+      currentPeriodStart,
+      currentPeriodEnd,
+      cancelAtPeriodEnd: subscription.cancel_at_period_end,
+      canceledAt: subscription.canceled_at ? new Date(subscription.canceled_at * 1000) : null,
+      trialEndsAt: subscription.trial_end ? new Date(subscription.trial_end * 1000) : null,
+    },
+  });
+}
+
+export async function handleSubscriptionDeleted(subscription: Stripe.Subscription): Promise<void> {
+  const existing = await prisma.subscription.findUnique({
+    where: { stripeSubscriptionId: subscription.id },
+  });
+  if (!existing) return;
+
+  await prisma.subscription.update({
+    where: { stripeSubscriptionId: subscription.id },
+    data: {
+      status: SubscriptionStatus.CANCELED,
+      cancelAtPeriodEnd: false,
+      canceledAt: subscription.canceled_at ? new Date(subscription.canceled_at * 1000) : new Date(),
+      updatedAt: new Date(),
+    },
+  });
+}
+
+export async function resolveUserIdFromStripeEvent(
+  subscription: Stripe.Subscription,
+): Promise<string | null> {
+  const metaUserId = subscription.metadata?.userId as string | undefined;
+  if (metaUserId) return metaUserId;
+
+  const customerId = typeof subscription.customer === 'string'
+    ? subscription.customer
+    : subscription.customer.id;
+
+  const existing = await prisma.subscription.findFirst({
+    where: { stripeCustomerId: customerId },
+    select: { userId: true },
+  });
+
+  return existing?.userId ?? null;
+}