feat(14-01): rewrite database foundation from SQLite to PostgreSQL

- Replace all 13 sqliteTable definitions with pgTable (pg-core)
- Convert integer timestamps to native timestamp type with defaultNow()
- Convert real columns to doublePrecision, integer used to boolean
- Rewrite db connection to use postgres.js driver with DATABASE_URL
- Rewrite migrate.ts to use postgres-js migrator targeting drizzle-pg/
- Convert seed.ts to async
- Update drizzle.config.ts to postgresql dialect
- Install postgres and @electric-sql/pglite, remove better-sqlite3

src/db/index.ts

@@ -1,9 +1,9 @@
-import { Database } from "bun:sqlite";
-import { drizzle } from "drizzle-orm/bun-sqlite";
+import { drizzle } from "drizzle-orm/postgres-js";
+import postgres from "postgres";
 import * as schema from "./schema.ts";
 
-const sqlite = new Database(process.env.DATABASE_PATH || "gearbox.db");
-sqlite.run("PRAGMA journal_mode = WAL");
-sqlite.run("PRAGMA foreign_keys = ON");
-
-export const db = drizzle(sqlite, { schema });
+const connectionString =
+	process.env.DATABASE_URL ||
+	"postgresql://gearbox:gearbox@localhost:5432/gearbox";
+const queryClient = postgres(connectionString);
+export const db = drizzle(queryClient, { schema });