Feat v0.2.4: SDK Topbar, Schedules surface, manifest icons, UserMenu cleanup

Shell navigation:
- sw.shell.Topbar — composable nav bar (title + slot + bell + user menu)
- Topbar CSS in sw-shell.css, wired into SDK via dynamic import

Schedules surface (packages/schedules/):
- Wraps kernel /api/v1/schedules CRUD + run + logs
- Table view with cron badge, human-readable preview, enable toggle
- Create/edit dialog with live cron-to-english preview

Manifest icons:
- icon field in manifest.json (emoji string)
- Surfaces API returns icon from package manifest
- UserMenu renders per-surface icons

UserMenu cleanup:
- Removed dead Chat/Notes/Projects hardcoded links
- Menu now driven by /api/v1/surfaces API (installed surfaces only)
- Core surfaces filtered via CORE_IDS set

Bug fixes:
- isAdmin() in can.js now checks surface.admin.access RBAC grant
  instead of deprecated user.role column (v0.2.0 regression)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/dashboard/manifest.json

@@ -5,6 +5,7 @@
   "version": "0.31.1",
   "tier": "browser",
   "author": "Switchboard Core",
+  "icon": "📊",
   "description": "Project dashboard exercising all SDK primitives",
   "route": "/s/dashboard",
   "permissions": [],