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/settings.py

@@ -9,6 +9,9 @@ from app.models.api_key import ApiKey
 
 bp = Blueprint('settings', __name__, url_prefix='/settings')
 
+VALID_APP_ROLES = {'admin', 'advanced', 'standard'}
+VALID_PORTAL_ROLES = {'admin', 'advanced', 'standard'}
+
 
 def _sync_user_to_app(app_id, username, role):
     """
@@ -76,7 +79,10 @@ def new_user():
         username = request.form.get('username', '').strip()
         email = request.form.get('email', '').strip()
         password = request.form.get('password', '')
-        is_admin = request.form.get('is_admin') == 'on'
+        portal_role = request.form.get('portal_role', 'standard').strip()
+        if portal_role not in VALID_PORTAL_ROLES:
+            portal_role = 'standard'
+        is_admin = portal_role == 'admin'  # kept for legacy checks
 
         if not username or not email or not password:
             flash('Username, email and password are required.', 'danger')
@@ -90,7 +96,7 @@ def new_user():
             username=username,
             email=email,
             password_hash=generate_password_hash(password),
-            is_admin=is_admin,
+            role=portal_role,
             is_active=True,
         )
         db.session.add(user)
@@ -99,7 +105,7 @@ def new_user():
         for app in registered_apps:
             app_id = app['id']
             role_val = request.form.get(f'role_{app_id}', 'none').strip()
-            if role_val in ('admin', 'user'):
+            if role_val in VALID_APP_ROLES:
                 db.session.add(AppAccess(user_id=user.id, app_name=app_id,
                                          is_active=True, app_role=role_val))
 
@@ -109,7 +115,7 @@ def new_user():
         for app in registered_apps:
             app_id = app['id']
             role_val = request.form.get(f'role_{app_id}', 'none').strip()
-            if role_val in ('admin', 'user'):
+            if role_val in VALID_APP_ROLES:
                 _sync_user_to_app(app_id, username, role_val)
 
         flash(f'User "{username}" created successfully.', 'success')
@@ -127,10 +133,10 @@ def update_access(user_id):
 
     for app in registered_apps:
         app_id = app['id']
-        # The UI sends role_<app_id> = 'admin' | 'user' | 'none'
+        # The UI sends role_<app_id> = 'admin' | 'advanced' | 'standard' | 'none'
         role_val = request.form.get(f'role_{app_id}', 'none').strip()
-        should_have = role_val in ('admin', 'user')
-        app_role = role_val if role_val in ('admin', 'user') else None
+        should_have = role_val in VALID_APP_ROLES
+        app_role = role_val if role_val in VALID_APP_ROLES else None
 
         existing = AppAccess.query.filter_by(user_id=user.id, app_name=app_id).first()
         if existing:
@@ -146,7 +152,7 @@ def update_access(user_id):
     for app in registered_apps:
         app_id = app['id']
         role_val = request.form.get(f'role_{app_id}', 'none').strip()
-        if role_val in ('admin', 'user'):
+        if role_val in VALID_APP_ROLES:
             _sync_user_to_app(app_id, user.username, role_val)
 
     flash(f'Access for "{user.username}" updated.', 'success')