feat: add auth crypto utilities (password hash, JWT, token hash)

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

server/auth.test.ts

@@ -0,0 +1,40 @@
+import { afterEach, describe, expect, it, setSystemTime } from 'bun:test'
+import { hashPassword, hashToken, signAccessToken, verifyAccessToken, verifyPassword } from './auth'
+
+afterEach(() => {
+  setSystemTime()
+})
+
+describe('auth utilities', () => {
+  it('hashes and verifies a password', async () => {
+    const hash = await hashPassword('secret123')
+    expect(await verifyPassword('secret123', hash)).toBe(true)
+    expect(await verifyPassword('wrong', hash)).toBe(false)
+  })
+
+  it('signs and verifies an access token', async () => {
+    const token = await signAccessToken('user1', 'admin', 'mysecret')
+    const payload = await verifyAccessToken(token, 'mysecret')
+    expect(payload).toEqual({ userId: 'user1', role: 'admin' })
+  })
+
+  it('returns null for an expired access token', async () => {
+    setSystemTime(new Date('2026-01-01T00:00:00.000Z'))
+    const token = await signAccessToken('user1', 'user', 'mysecret')
+
+    setSystemTime(new Date('2026-01-01T00:16:00.000Z'))
+    const payload = await verifyAccessToken(token, 'mysecret')
+    expect(payload).toBeNull()
+  })
+
+  it('returns null for an access token with wrong secret', async () => {
+    const token = await signAccessToken('user1', 'user', 'mysecret')
+    const payload = await verifyAccessToken(token, 'wrongsecret')
+    expect(payload).toBeNull()
+  })
+
+  it('hashToken is deterministic', () => {
+    expect(hashToken('abc')).toBe(hashToken('abc'))
+    expect(hashToken('abc')).not.toBe(hashToken('xyz'))
+  })
+})