feat(db): drizzle schema (settings, sessions) + boot migrations

server/test/db.test.ts

@@ -0,0 +1,16 @@
+import { describe, expect, test } from "bun:test";
+import { mkdtempSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { openDb } from "../src/db";
+import { settings } from "../src/db/schema";
+
+describe("db", () => {
+  test("opens, migrates, round-trips a setting", async () => {
+    const dir = mkdtempSync(join(tmpdir(), "helios-"));
+    const db = openDb(dir);
+    await db.insert(settings).values({ key: "llm_base_url", value: "https://openrouter.ai/api/v1" });
+    const rows = await db.select().from(settings);
+    expect(rows).toEqual([{ key: "llm_base_url", value: "https://openrouter.ai/api/v1" }]);
+  });
+});