Add Drizzle + Postgres setup (task 03)

drizzle-orm + postgres driver + drizzle-kit wired up. Core schema declares
users, households, and household_members. docker-compose.dev.yaml runs
Postgres 16 locally. Initial migration generated and verified applied.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/db.ts

@@ -0,0 +1,6 @@
+import { drizzle } from "drizzle-orm/postgres-js";
+import postgres from "postgres";
+
+const client = postgres(process.env["DATABASE_URL"]!);
+
+export const db = drizzle(client);

src/modules/_core/schema.ts

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+import { pgEnum, pgTable, primaryKey, timestamp, uuid, varchar } from "drizzle-orm/pg-core";
+
+export const roleEnum = pgEnum("household_member_role", ["owner", "member"]);
+
+export const users = pgTable("users", {
+  id: uuid("id").primaryKey().defaultRandom(),
+  email: varchar("email", { length: 255 }).notNull().unique(),
+  displayName: varchar("display_name", { length: 255 }).notNull(),
+  createdAt: timestamp("created_at", { withTimezone: true }).notNull().defaultNow(),
+});
+
+export const households = pgTable("households", {
+  id: uuid("id").primaryKey().defaultRandom(),
+  name: varchar("name", { length: 255 }).notNull(),
+  createdAt: timestamp("created_at", { withTimezone: true }).notNull().defaultNow(),
+});
+
+export const householdMembers = pgTable(
+  "household_members",
+  {
+    householdId: uuid("household_id")
+      .notNull()
+      .references(() => households.id, { onDelete: "cascade" }),
+    userId: uuid("user_id")
+      .notNull()
+      .references(() => users.id, { onDelete: "cascade" }),
+    role: roleEnum("role").notNull().default("member"),
+  },
+  (t) => [primaryKey({ columns: [t.householdId, t.userId] })],
+);