Add Umami analytics, subscription tiers, tool-call metering

- Analytics: <Analytics /> in root layout loads umami when NEXT_PUBLIC_UMAMI_* env are set
- Subscription: free/pro tiers in Postgres, daily quotas (10msg/5tool free, 1000/500 pro)
- Chat route: checkAndConsume(chat_message) gate before streamText, 429 when exhausted
- Tool metering: getWeather wrapped with withLimit decorator that deducts tool_call quota
- Pricing page at /pricing with upgrade button
- /api/billing/checkout posts to EGBE payment gateway, /api/billing/webhook verifies HMAC and upgrades user on checkout.session.completed
- UsageBadge in chat header polls /api/usage every 15s
- Dropped now-unused entitlements.ts

lib/db/schema.ts

@@ -1,6 +1,7 @@
 import type { InferSelectModel } from "drizzle-orm";
 import {
   boolean,
+  integer,
   json,
   pgTable,
   primaryKey,
@@ -68,3 +69,49 @@ export const vote = pgTable(
 );
 
 export type Vote = InferSelectModel<typeof vote>;
+
+export const subscription = pgTable("Subscription", {
+  userId: uuid("userId")
+    .primaryKey()
+    .notNull()
+    .references(() => user.id),
+  tier: varchar("tier", { enum: ["free", "pro"] })
+    .notNull()
+    .default("free"),
+  status: varchar("status", { enum: ["active", "canceled", "past_due"] })
+    .notNull()
+    .default("active"),
+  stripeCustomerId: text("stripeCustomerId"),
+  stripeSubscriptionId: text("stripeSubscriptionId"),
+  currentPeriodEnd: timestamp("currentPeriodEnd"),
+  createdAt: timestamp("createdAt").notNull().defaultNow(),
+  updatedAt: timestamp("updatedAt").notNull().defaultNow(),
+});
+
+export type Subscription = InferSelectModel<typeof subscription>;
+
+export const usage = pgTable(
+  "Usage",
+  {
+    userId: uuid("userId")
+      .notNull()
+      .references(() => user.id),
+    periodKey: varchar("periodKey", { length: 10 }).notNull(),
+    messageCount: integer("messageCount").notNull().default(0),
+    toolCallCount: integer("toolCallCount").notNull().default(0),
+    updatedAt: timestamp("updatedAt").notNull().defaultNow(),
+  },
+  (table) => ({
+    pk: primaryKey({ columns: [table.userId, table.periodKey] }),
+  })
+);
+
+export type Usage = InferSelectModel<typeof usage>;
+
+export const webhookEvent = pgTable("WebhookEvent", {
+  id: text("id").primaryKey().notNull(),
+  type: text("type").notNull(),
+  receivedAt: timestamp("receivedAt").notNull().defaultNow(),
+});
+
+export type WebhookEvent = InferSelectModel<typeof webhookEvent>;