Add database schema and Kysely packages

- Create initial database migration with full auth schema:
  - users, sessions, passkeys, devices tables
  - orgs, org_members, org_sites, org_invites tables
  - email_verifications, password_resets, login_requests tables
  - Indexes for common lookups and cleanup jobs
- Add @reviq/db-schema package with kysely-codegen
- Add @reviq/db package with Kysely client

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/db/src/client.ts

@@ -0,0 +1,37 @@
+/**
+ * Kysely database client
+ *
+ * @module @reviq/db
+ */
+
+import { Kysely, PostgresDialect } from "kysely";
+import type { Database } from "@reviq/db-schema";
+import pg from "pg";
+
+const { Pool } = pg;
+
+/**
+ * Creates a new Kysely database client
+ *
+ * @param connectionString - PostgreSQL connection string (defaults to DATABASE_URL env var)
+ * @returns Kysely database instance
+ */
+export const createDb = (
+  connectionString: string = process.env.DATABASE_URL || ""
+): Kysely<Database> => {
+  if (!connectionString) {
+    throw new Error(
+      "Database connection string is required. Set DATABASE_URL environment variable."
+    );
+  }
+
+  const dialect = new PostgresDialect({
+    pool: new Pool({
+      connectionString,
+    }),
+  });
+
+  return new Kysely<Database>({
+    dialect,
+  });
+};