slides: grantable slides.manage permission for non-admin curators

plugins/slides/plugin.py

@@ -58,14 +58,25 @@ class SlidesPlugin(BasePlugin):
         """Slide playlist metadata (image files live on disk)."""
         return [TvSlide]
 
+    def get_permissions(self) -> List:
+        """RBAC permission for curating slides (both surfaces). Grantable to a
+        non-admin role so a curator can manage the lobby TV + screensaver
+        without full admin. Admins hold it by default."""
+        return [
+            ('slides.manage',
+             'Manage lobby display and screensaver slides', 'slides'),
+        ]
+
     def get_navigation_items(self) -> List[Dict]:
-        """Sidebar entry for the slide manager (admin)."""
+        """Sidebar entry for the slide manager. Gated on slides.manage so only a
+        curator (or admin, who holds it by default) sees the link."""
         return [
             {
                 'name': 'Slides',
                 'icon': 'image',
                 'route': '/settings/slides',
                 'position': 7,
+                'permission': 'slides.manage',
             },
         ]