Fix project detail milestones fetch + reset-apikey UI

- Fix: ProjectDetailPage now uses /projects/{id}/milestones instead of /milestones?project_id={code} (fixes 422)
- Add: Reset API Key button on UsersPage with permission-based visibility
- Add: One-time key display with copy-to-clipboard
- Protect admin and acc-mgr accounts from deletion in UI

src/pages/ProjectDetailPage.tsx

@@ -26,7 +26,7 @@ export default function ProjectDetailPage() {
   const fetchProject = () => {
     api.get<Project>(`/projects/${id}`).then(({ data }) => setProject(data))
     api.get<ProjectMember[]>(`/projects/${id}/members`).then(({ data }) => setMembers(data))
-    api.get<Milestone[]>(`/milestones?project_id=${id}`).then(({ data }) => setMilestones(data))
+    api.get<Milestone[]>(`/projects/${id}/milestones`).then(({ data }) => setMilestones(data))
   }
 
   useEffect(() => {