feat: restrict backup archive download to primary admin and hide admin-hidden projects from other admins

- Add `get_admin_uids()` and `get_primary_admin_uid()` to database.py for resolving the earliest-created admin
- Modify `can_view_project()` in content.py so a project hidden by an admin is invisible to other admins (both web UI and REST API)
- Update `_download_url()` and `_backup_payload()` in admin/backups.py to accept a `can_download` flag, gating the download endpoint with `is_primary_admin()`
- Remove `role` from `_user_facts()` in docs_live.py to avoid leaking admin status in live docs
- Update doc summaries in docs_api.py to reflect the new admin-visibility and backup-download semantics

devplacepy/templates/base.html

@@ -94,7 +94,7 @@
                         <img src="{{ avatar_url('multiavatar', user['username'], 32) }}" class="avatar-img avatar-sm" alt="{{ user['username'] }}" loading="lazy">
                         <div class="topnav-user-info">
                             <span class="topnav-user-name">{{ user['username'] }}</span>
-                            {% if is_admin(user) %}<span class="topnav-user-role">{{ user['role'] }}</span>{% endif %}
+                            <span class="topnav-user-level">Level {{ user.get('level', 1) }}</span>
                         </div>
                     </button>
                     <div class="dropdown-menu">
@@ -150,7 +150,7 @@
                 <img src="{{ avatar_url('multiavatar', user['username'], 32) }}" class="avatar-img avatar-sm" alt="{{ user['username'] }}" loading="lazy">
                 <div class="topnav-mobile-user-info">
                     <span>{{ user['username'] }}</span>
-                    {% if is_admin(user) %}<span class="topnav-mobile-user-role">{{ user['role'] }}</span>{% endif %}
+                    <span class="topnav-mobile-user-level">Level {{ user.get('level', 1) }}</span>
                 </div>
             </div>
             <a href="/profile/{{ user['username'] }}" class="topnav-mobile-link"><span class="icon">👤</span> Profile</a>