Add embedded PGlite support as zero-config database option

Add @electric-sql/pglite so the server can run without an external
Postgres instance. When DATABASE_URL is not set, the server auto-creates
an embedded PGlite database in ./data/pglite with schema push on startup.

- Add createPgliteDb() alongside the existing createDb()
- Make DATABASE_URL optional in server config
- Update drizzle config to glob schema files
- Update migrate script to support both Postgres and PGlite
- Add data/ to .gitignore for local PGlite storage

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

packages/db/src/client.ts

@@ -1,10 +1,26 @@
-import { drizzle } from "drizzle-orm/postgres-js";
+import { mkdirSync } from "node:fs";
+import { drizzle as drizzlePg } from "drizzle-orm/postgres-js";
+import { drizzle as drizzlePglite } from "drizzle-orm/pglite";
 import postgres from "postgres";
+import { PGlite } from "@electric-sql/pglite";
 import * as schema from "./schema/index.js";
 
 export function createDb(url: string) {
   const sql = postgres(url);
-  return drizzle(sql, { schema });
+  return drizzlePg(sql, { schema });
+}
+
+export async function createPgliteDb(dataDir: string) {
+  mkdirSync(dataDir, { recursive: true });
+  const client = new PGlite(dataDir);
+  const db = drizzlePglite({ client, schema });
+
+  // Auto-push schema to PGlite on startup (like drizzle-kit push)
+  const { pushSchema } = await import("drizzle-kit/api");
+  const { apply } = await pushSchema(schema, db as any);
+  await apply();
+
+  return db;
 }
 
 export type Db = ReturnType<typeof createDb>;