feat(db): add Drizzle ORM with local SQLite storage

Configure Bun SQLite with WAL mode, foreign keys, and a shared database path for development and production.

Add migration commands and startup migration handling, check database connectivity in the health endpoint, and document configuration while excluding local database files from Git.

src/db/config.ts

@@ -0,0 +1,4 @@
+import { resolve } from "node:path";
+
+// Relative paths are resolved from the project root when running package scripts.
+export const databasePath = resolve(process.env.DATABASE_PATH ?? "data/minabot.sqlite");

src/db/index.ts

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+import { Database } from "bun:sqlite";
+import { mkdirSync } from "node:fs";
+import { dirname } from "node:path";
+import { drizzle } from "drizzle-orm/bun-sqlite";
+import { databasePath } from "./config";
+import * as schema from "./schema";
+
+mkdirSync(dirname(databasePath), { recursive: true });
+
+export const sqlite = new Database(databasePath, { create: true, strict: true });
+sqlite.exec("PRAGMA journal_mode = WAL;");
+sqlite.exec("PRAGMA foreign_keys = ON;");
+sqlite.exec("PRAGMA busy_timeout = 5000;");
+
+export const db = drizzle(sqlite, { schema });
+
+if (import.meta.hot) {
+  import.meta.hot.dispose(() => sqlite.close());
+}

src/db/schema.ts

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+// Define application tables here with drizzle-orm/sqlite-core.
+export {};