feat: remove dev_session, add Drizzle schema + RLS + real auth

BREAKING: dev_session cookie bypass removed. Admin access now requires
a real Auth.js v5 session (Google OAuth in production). Provision users
by inserting into users + tenant_users tables.

New in this commit:
- db/migrations/0001_init.sql: 18-table SaaS schema with RLS (tenants,
  users, tenant_users, plans, add_ons, subscriptions, tenant_add_ons,
  products, product_images, stops, customers, orders, order_items,
  brand_settings, email_templates, campaigns, files, audit_log)
- db/schema/: Drizzle TypeScript mirror of every table
- db/client.ts: withTenant() / withPlatformAdmin() query wrappers that
  set Postgres GUCs (app.current_tenant_id, app.platform_admin) for
  RLS enforcement. Never query a tenant-scoped table without one.
- db/seed.ts: seeds 3 plans, 6 add-ons, 2 tenants (Tuxedo, Indian River
  Direct), brand_settings, sample products/stops/customers
- scripts/migrate.js: applies migrations in lexical order with tracking
- scripts/db-reset.js: drops + recreates DB, runs migrate + seed
- DATABASE_URL now uses rc_app (non-superuser, NOBYPASSRLS). RLS is
  enforced even for the app user. DATABASE_ADMIN_URL for migrations.
- src/lib/admin-permissions.ts: getAdminUser() reads Auth.js session,
  looks up user + tenant in Postgres. brand_id kept as alias for
  backward compat.
- src/middleware.ts: Auth.js-only route protection, dev_session gone
- src/app/login/LoginClient.tsx: Google OAuth only, no demo mode
- src/components/admin/AdminSidebar.tsx + AdminHeader.tsx: signOutAction
  replaces supabase signout
- @/db/* path aliases in tsconfig.json + vitest.config.ts
- drizzle.config.ts added
- db/auth_schema.sql removed (was a stub; replaced by real schema)
- src/app/api/dev-login/route.ts deleted
- tests: updated to remove dev_session coverage

db/schema/customers.ts

@@ -0,0 +1,45 @@
+/**
+ * Customers. Source of truth: `db/migrations/0001_init.sql`.
+ */
+import {
+  pgTable,
+  uuid,
+  text,
+  boolean,
+  timestamp,
+  index,
+  uniqueIndex,
+} from "drizzle-orm/pg-core";
+import { sql } from "drizzle-orm";
+import { tenants } from "./tenants";
+
+export const customers = pgTable(
+  "customers",
+  {
+    id: uuid("id").primaryKey().defaultRandom(),
+    tenantId: uuid("tenant_id")
+      .notNull()
+      .references(() => tenants.id, { onDelete: "cascade" }),
+    name: text("name").notNull(),
+    email: text("email"),
+    phone: text("phone"),
+    smsOptIn: boolean("sms_opt_in").notNull().default(false),
+    emailOptIn: boolean("email_opt_in").notNull().default(true),
+    notes: text("notes"),
+    createdAt: timestamp("created_at", { withTimezone: true })
+      .notNull()
+      .defaultNow(),
+    updatedAt: timestamp("updated_at", { withTimezone: true })
+      .notNull()
+      .defaultNow(),
+  },
+  (t) => ({
+    tenantIdx: index("customers_tenant_idx").on(t.tenantId),
+    emailIdx: uniqueIndex("customers_tenant_email_idx")
+      .on(t.tenantId, t.email)
+      .where(sql`${t.email} IS NOT NULL`),
+  }),
+);
+
+export type Customer = typeof customers.$inferSelect;
+export type NewCustomer = typeof customers.$inferInsert;