feat: 3-tier role system across all platform apps

Portal:
- Replace is_admin boolean with role column (admin/advanced/standard)
- Settings UI: 3-tier portal role select + per-app role dropdowns
- /portal-return endpoint: re-establishes session from JWT for sub-app back-links
- /api/internal/nv-users: internal endpoint for NetworkView user sync
- portal/migrate_roles.py: one-time DB migration script
- Role badges (admin/advanced/standard) in topbar and settings table

DigiServer:
- Add editor and viewer roles (portal advanced->editor, standard->viewer)
- PlaylistPermission model: grant viewer users edit access to specific playlists
- app/utils/access.py: shared editor_required, admin_required, can_edit_playlist helpers
- Content routes: editor_required on create/delete, per-playlist permission check on mutations
- Admin: playlist_permissions route + template to manage viewer playlist grants
- Base template: hide Admin nav for viewers, Portal button (⬡) returns to portal
- content_list_new: hide create/delete for viewers; Manage vs View button per permission
- manage_playlist_content: view-only mode when user lacks edit permission

NetworkView:
- backend/src/middleware/rbac.js: requireRole + requireWriteAccess helpers
- site_permissions table: one site per advanced user
- All mutating routes guarded (admin=all, advanced=assigned site, viewer=read-only)
- Portal SSO auto-upsert: user row synced from X-Auth-Role on every request
- GET /api/users: merges portal users list with local NV data (all 4 portal users visible)
- GET/PUT /api/users/:id/site-permission: assign site to advanced user
- Settings Users tab: role badges, site dropdown for advanced, (portal only) indicator
- Sidebar: ⬡ Portal button between Settings and Logout
- Frontend build: VITE_API_BASE=/networkview/api now set in start-dev.sh

IT Assets / Server Monitor:
- portal_sso.py updated: map advanced->editor/viewer, standard->readonly
- AdminUser model: add editor role + is_editor property

portal/app/routes/api.py

@@ -1,5 +1,6 @@
-from flask import Blueprint, request, make_response, current_app
+from flask import Blueprint, request, make_response, current_app, jsonify
 import jwt
+import secrets as _secrets
 
 bp = Blueprint('api', __name__, url_prefix='/api')
 
@@ -70,3 +71,38 @@ def _app_from_uri(uri):
     if uri.startswith('/srvmonitor/'):
         return 'srvmonitor'
     return None
+
+
+@bp.route('/internal/nv-users')
+def nv_users_internal():
+    """
+    Internal endpoint for the NetworkView backend to fetch all portal users
+    that have NetworkView access, together with their assigned NV role.
+    Protected by X-Internal-Token header (shared INTERNAL_SYNC_SECRET).
+    """
+    secret = current_app.config.get('INTERNAL_SYNC_SECRET', '')
+    provided = request.headers.get('X-Internal-Token', '')
+    if not secret or not _secrets.compare_digest(provided, provided and secret):
+        # constant-time compare — reject if secret mismatch or empty
+        if not secret or not provided or not _secrets.compare_digest(provided, secret):
+            return jsonify({'error': 'forbidden'}), 403
+
+    from app.models.user import PortalUser
+    from app.models.app_access import AppAccess
+
+    users = PortalUser.query.filter_by(is_active=True).order_by(PortalUser.username).all()
+    result = []
+    for u in users:
+        nv_access = AppAccess.query.filter_by(
+            user_id=u.id, app_name='networkview', is_active=True
+        ).first()
+        if nv_access is None:
+            continue  # skip users who have no NV access at all
+        result.append({
+            'portal_id':   str(u.id),
+            'username':    u.username,
+            'email':       u.email,
+            'portal_role': u.role,
+            'nv_role':     nv_access.app_role or u.role,  # per-app override or portal role
+        })
+    return jsonify(result)