feat(tests): add unit and integration test suite (node:test)

Adds 215 tests across three tiers using node:test + node:assert/strict
(no new test framework dependencies):

- test/tools/ — middleware and utility tests (token, hash, authenticate,
  jsonBody, convertError, validators)
- test/shared/ — DbInterface/BackendDbInterface contract suites reusable
  across backends (users, abodes, residents, apikeys, sessions, auth)
- test/backends/sqlite/ — SQLite-private tests (sql builder, WrappedDb,
  migrator) + shared suites via SqliteInterface
- test/backends/api/ — ApiInterface unit tests + shared suites via a
  live Koa server backed by SQLite

Also fixes four bugs uncovered by the tests:
- ApiInterface: path params leaked into query string (slice(1) fix)
- ApiInterface: calling res.json() on 204 No Content responses
- SqliteInterface.updateResident: missing comma in SET clause
- WrappedBetterSqlite3Db: readonly:undefined rejected by better-sqlite3

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

test/shared/sessions.ts

@@ -0,0 +1,65 @@
+import { describe, it, before, after } from "node:test";
+import assert from "node:assert/strict";
+import type { BackendDbInterface } from "../../src/db/types/DbInterface.js";
+import { NotFoundAbodeError } from "../../src/db/types/errors.js";
+import { hashPassword } from "../../src/util/hash.js";
+
+export function runSessionTests(
+  name: string,
+  getDb: () => Promise<{ db: BackendDbInterface; close(): void }>
+): void {
+  describe(`${name}: sessions`, async () => {
+    let db: BackendDbInterface;
+    let close: () => void;
+    let uid: string;
+
+    before(async () => {
+      ({ db, close } = await getDb());
+      const pw = await hashPassword("session-password");
+      const user = await db.createUser({
+        email: `session-user-${Date.now()}@test.example`,
+        name: "Session User",
+        password: pw,
+        flags: {},
+      });
+      uid = user.uid;
+    });
+
+    after(() => close());
+
+    it("createSession returns an as_ token", async () => {
+      const token = await db.createSession(uid);
+      assert.ok(token.startsWith("as_"), `token starts with as_: ${token}`);
+      assert.equal(token.length, 35, "as_ + 32 hex chars");
+    });
+
+    it("getUserBySession returns the correct user", async () => {
+      const token = await db.createSession(uid);
+      const user = await db.getUserBySession(token);
+      assert.equal(user.uid, uid);
+    });
+
+    it("getUserBySession throws NotFoundAbodeError for unknown token", async () => {
+      const fakeToken = `as_${"0".repeat(32)}` as `as_${string}`;
+      await assert.rejects(
+        () => db.getUserBySession(fakeToken),
+        (err) => {
+          assert.ok(err instanceof NotFoundAbodeError);
+          return true;
+        }
+      );
+    });
+
+    it("deleteSessionsByUser invalidates all sessions for user", async () => {
+      const token = await db.createSession(uid);
+      await db.deleteSessionsByUser(uid);
+      await assert.rejects(
+        () => db.getUserBySession(token),
+        (err) => {
+          assert.ok(err instanceof NotFoundAbodeError);
+          return true;
+        }
+      );
+    });
+  });
+}