Add MSW infrastructure: handlers, fixtures, request-log, and Vitest setup

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

src/mocks/fixtures/my-account.json

@@ -0,0 +1,9 @@
+{
+  "username": "testadmin",
+  "name": "Test Admin",
+  "is_sso": false,
+  "created_at": "2025-01-15T10:00:00Z",
+  "roles": [
+    { "code": "admin", "name": "Administrator" }
+  ]
+}