refactor: break monorepo into 3 standalone services (gateway, backend, frontend)

- Remove pnpm workspace, moon repo, and all monorepo tooling
- Delete packages/shared/, embed shared code directly into each service
- Copy packages/shared/src/* -> services/backend/src/shared/ and services/discord-gateway/src/shared/
- Replace all @bete/shared imports with @/shared/ path alias
- Remove @bete/shared workspace dependency from both services
- Update root package.json scripts from --filter to --prefix
- Rewrite Dockerfiles to build each service standalone
- Clean up biome.json, .gitignore, remove root drizzle.config.ts

services/discord-gateway/src/shared/database/pool.ts

@@ -0,0 +1,36 @@
+import { type PoolConfig as PgPoolConfig, Pool } from "pg";
+
+export interface PoolConfig {
+  url?: string;
+  host?: string;
+  port?: number;
+  user?: string;
+  password?: string;
+  database?: string;
+  min?: number;
+  max?: number;
+}
+
+export function createPoolFromConfig(cfg: PoolConfig): Pool {
+  const opts: PgPoolConfig = {
+    min: cfg.min ?? 2,
+    max: cfg.max ?? 10,
+  };
+
+  if (cfg.url) {
+    opts.connectionString = cfg.url;
+  } else {
+    opts.host = cfg.host;
+    opts.port = cfg.port;
+    opts.user = cfg.user;
+    opts.password = cfg.password;
+    opts.database = cfg.database;
+  }
+
+  return new Pool(opts);
+}
+
+export function closePool(pool: Pool | null): Promise<void> {
+  if (!pool) return Promise.resolve();
+  return pool.end();
+}