feat: remove nginx, add projects/milestones/notifications pages

- Dockerfile: replace nginx with serve for static files
- Fix auth endpoint: /auth/login → /auth/token
- Add ProjectsPage, ProjectDetailPage
- Add MilestonesPage, MilestoneDetailPage with progress bar
- Add NotificationsPage with unread count
- Sidebar: add milestones/notifications nav, live unread badge
- API: configurable VITE_API_BASE for host nginx proxy
- Types: add Milestone, MilestoneProgress, Notification, ProjectMember

nginx.conf

@@ -1,15 +0,0 @@
-server {
-    listen 3000;
-    root /usr/share/nginx/html;
-    index index.html;
-
-    location /api/ {
-        proxy_pass http://backend:8000/;
-        proxy_set_header Host $host;
-        proxy_set_header X-Real-IP $remote_addr;
-    }
-
-    location / {
-        try_files $uri $uri/ /index.html;
-    }
-}