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

digiserver-v2/app/utils/portal_sso.py

@@ -3,7 +3,12 @@ Portal SSO middleware for DigiServer v2.
 
 When the umbrella nginx verifies the portal JWT it sets two headers:
   X-Auth-Username  — the portal username
-  X-Auth-Role      — 'admin' or 'user'
+  X-Auth-Role      — 'admin' | 'advanced' | 'standard'
+
+Portal role → DigiServer local role mapping:
+  admin    → admin   (full access including user management)
+  advanced → editor  (manage content/playlists, no user management)
+  standard → viewer  (read-only)
 
 This before_request handler reads those headers and auto-logs in the
 corresponding local DigiServer user, creating them on first access if
@@ -32,12 +37,21 @@ def init_portal_sso(app):
             login_user(user, remember=False)
 
 
+def _portal_role_to_local(portal_role):
+    """Map a portal role string to the DigiServer local role."""
+    if portal_role == 'admin':
+        return 'admin'
+    if portal_role == 'advanced':
+        return 'editor'
+    return 'viewer'  # 'standard' or anything unknown
+
+
 def _get_or_create_user(username, role):
     from app.models.user import User
     from app.extensions import db, bcrypt
 
     try:
-        target_role = 'admin' if role == 'admin' else 'user'
+        target_role = _portal_role_to_local(role)
         user = User.query.filter_by(username=username).first()
         if not user:
             hashed_pw = bcrypt.generate_password_hash(secrets.token_hex(32)).decode('utf-8')