Add Cypress E2E tests with fixture-based API mocking for UI regression protection

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

cypress/fixtures/api/files.json

@@ -0,0 +1,42 @@
+[
+  {
+    "type": "log",
+    "id": 1,
+    "name": "sample-process.xes",
+    "parent": null,
+    "owner": { "username": "testadmin", "name": "Test Admin" },
+    "updated_at": "2025-06-10T14:30:00Z",
+    "accessed_at": "2025-06-12T09:00:00Z",
+    "is_deleted": false
+  },
+  {
+    "type": "filter",
+    "id": 10,
+    "name": "filtered-sample",
+    "parent": { "type": "log", "id": 1, "name": "sample-process.xes" },
+    "owner": { "username": "testadmin", "name": "Test Admin" },
+    "updated_at": "2025-06-11T08:00:00Z",
+    "accessed_at": "2025-06-12T10:00:00Z",
+    "is_deleted": false
+  },
+  {
+    "type": "log",
+    "id": 2,
+    "name": "production-log.csv",
+    "parent": null,
+    "owner": { "username": "user1", "name": "Alice Wang" },
+    "updated_at": "2025-06-09T16:00:00Z",
+    "accessed_at": null,
+    "is_deleted": false
+  },
+  {
+    "type": "log-check",
+    "id": 100,
+    "name": "conformance-check-1",
+    "parent": { "type": "log", "id": 1, "name": "sample-process.xes" },
+    "owner": { "username": "testadmin", "name": "Test Admin" },
+    "updated_at": "2025-06-11T12:00:00Z",
+    "accessed_at": null,
+    "is_deleted": false
+  }
+]