Initial boilerplate scaffold for continuum-backend

Bun + ElysiaJS control plane: Drizzle/Postgres schema (printers, farms,
print_jobs, pgvector frame_embeddings), R2 presigned URLs, Redis Streams
frame ingestion queue, REST routes, and the /ws/edge/v1 edge-gateway
WebSocket uplink.

src/db/index.ts

@@ -0,0 +1,18 @@
+import { drizzle } from "drizzle-orm/postgres-js";
+import postgres from "postgres";
+import * as schema from "./schema";
+
+// Points at pgCat/PgBouncer, not Postgres directly, so keep prepared
+// statements disabled and cap the pool per-instance connections low.
+const connectionString = process.env.DATABASE_URL;
+if (!connectionString) {
+  throw new Error("DATABASE_URL is not set");
+}
+
+const client = postgres(connectionString, {
+  prepare: false,
+  max: Number(process.env.DATABASE_POOL_MAX ?? 10),
+});
+
+export const db = drizzle(client, { schema });
+export type Database = typeof db;