test(api): stop tests leaking module mocks and env into later files

CI failed on a different set of tests each run because bun runs every test
file in one process and the file order differs between machines:

- the secretsmanager route test replaced the whole ../aws module, so files
  loaded after it lost awsClients, lambda and defaultAccountId (API Gateway,
  SES)
- the Lightsail tests restored FLOCI_ENDPOINT by assigning undefined, which
  stores the string "undefined" (runtime diagnostics)
- the auth tests used full-strength argon2 for ~30 sign-ins and timed out on
  slower runners; the OIDC cleanup test cached a discovery document without
  userinfo_endpoint for the shared issuer

Checked with 20 runs under bun test --randomize.

packages/api/src/auth.test.ts

@@ -13,7 +13,9 @@ const realFetch = globalThis.fetch
 let passwordHash: string
 
 beforeAll(async () => {
-    passwordHash = await Bun.password.hash('correct-horse-battery')
+    // Cheap parameters keep the many sign-in attempts below fast on slow CI runners; verification
+    // reads the parameters from the hash, so the code under test is unchanged.
+    passwordHash = await Bun.password.hash('correct-horse-battery', {algorithm: 'argon2id', memoryCost: 1024, timeCost: 1})
 })
 
 afterEach(() => {
@@ -239,7 +241,8 @@ describe('auth state cleanup', () => {
     test('caps pending OIDC requests and sweeps expired state', async () => {
         const config = authConfig(oidcEnv({FLOCI_UI_OIDC_ALLOW_ALL_USERS: 'true'}))
         const hono = app(config)
-        globalThis.fetch = (async () => Response.json({authorization_endpoint: 'https://idp.test/authorize', token_endpoint: 'https://idp.test/token', jwks_uri: 'https://idp.test/jwks'})) as unknown as typeof fetch
+        // The same document as mockIdp: discovery is cached per issuer for the rest of the run.
+        globalThis.fetch = (async () => Response.json({authorization_endpoint: 'https://idp.test/authorize', token_endpoint: 'https://idp.test/token', jwks_uri: 'https://idp.test/jwks', userinfo_endpoint: 'https://idp.test/userinfo'})) as unknown as typeof fetch
         for (let index = 0; index < 1_050; index++) await request(hono, '/api/auth/oidc/login', `10.1.${Math.floor(index / 250)}.${index % 250}`)
 
         expect(authStateSizes().oidcRequests).toBe(1_000)