Add comprehensive WebAuthn e2e/unit tests and virtual authenticator package

- Create @reviq/virtual-authenticator package with cryptographically valid
  WebAuthn credential generation for testing
- Add e2e tests for WebAuthn registration, authentication, passkey management
- Add unit tests for passkey-helpers and VirtualAuthenticator
- Add security tests for counter replay and tampered responses
- Configure test database environment in devenv.nix
- Add turbo.json test tasks and workspace configuration

Test results: 98 tests passing (54 virtual-authenticator, 25 e2e, 19 unit)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

package.json

@@ -3,7 +3,8 @@
   "private": true,
   "workspaces": [
     "apps/*",
-    "packages/*"
+    "packages/*",
+    "packages/testing/*"
   ],
   "scripts": {
     "dev": "turbo dev",