Fix bugs, migrate favorites store to Composition API, DRY state loader, add page tests, replace CSS vars with kit classes

Move unassign into a dedicated confirm dialog and fix icon ...

- Revert useAreaAssign composable back to pure assign logic; remove
  submitUnassignCore and unassign state that leaked into the assign modal.
- DeviceDetailPage, ScriptDetailPage, AreaDetailPage:
  * Remove the Unassign button from the assign modal footer.
  * Add a separate GnModal confirm dialog for unassign (like Remove).
  * Dropdown action now opens the confirm dialog instead of firing
    immediately.
  * Replace non-existent ph-map-pin-slash icon with ph-x-circle.

Show warning in assign modal for the last root area ...

Instead of hiding the assign UI, keep the button/menu item visible.
When the user opens the assign modal for the last root area, show a
GnAlert warning inside the modal explaining that it cannot be assigned.
The Assign button is hidden in this state; only Cancel (and Unassign if
applicable) remain. Backend guard in assignToArea stays as a fail-safe.

Add unassign action to area, device and script detail pages ...

- useAreaAssign composable: add submitUnassignCore and loading/error states.
- DeviceDetailPage: add 'Unassign from area' button inside assign modal and
  in the actions dropdown when device has an area_id.
- ScriptDetailPage: same for scripts (non-scope) with area_id.
- AreaDetailPage: add 'Unassign from parent' in assign modal and dropdown
  when area has a parent_id > 0.

Prevent assigning the last root area as a child ...

- Store: assignToArea now rejects with an error if the target area is the
  last remaining root (parent_id <= 0), preventing zero-root trees.
- UI: AreaDetailPage hides the 'Assign to area' / 'Change parent area'
  button and action-menu item when the current area is the last root,
  and shows an explanatory empty-state message instead.
- Tests: add coverage for both the rejection and the allowed case.

Use gnexus-ui-kit semantic colors for device status dot and add state components ...

- Status dot in DeviceTable now uses .text-success / .text-danger from
  gnexus-ui-kit with currentColor for background and glow instead of
  project-specific CSS vars.
- Add DeviceChannelsState component for per-channel state rendering.
- Add loadStatesFor helper in devices store for targeted state loading.
- Record styling rule in CLAUDE.md: always prefer kit color classes.

Replace connect column with inline status dot in device table

Make toast backgrounds opaque for readability

Show per-channel device states in DeviceTable and load states on AreaDetailPage

Add toast feedback for device reboot in list and detail views

Fix area assignment button on detail pages ...

- Rename submitAssign -> submitAssignCore in useAreaAssign composable
  to avoid name collision with local page handlers.
- Rename local page handlers -> handleAssignSubmit on Area, Device,
  and Script detail pages so event bindings call the wrapper correctly.
- Fix AppEmptyState.vue to forward #action slot into GnEmptyState's
  #actions slot so the Assign button renders for unassigned items.

Phase 5: Extract reusable useAsyncRequest composable for stores ...

- Add src/composables/useAsyncRequest.js to manage isLoading/error/AbortController
- Convert Pinia stores to Setup Stores: areas, devices, scripts, scanning
- Use useAsyncRequest for all simple list/detail loaders
- Fix API modules to forward options/signal (areas.devices, areas.scripts,
  devices.detail, scripts.scopeCode) — previously AbortControllers were
  created but signals were never passed to fetch
- Keep batch loadDeviceStates and reboot/runScript as custom logic
- Use immutable Set updates for reactive rebootingIds/runningAliases
- Update modules.spec.js assertions for new optional arguments
- Add 9 unit tests for useAsyncRequest

All 139 tests pass.

Improve AppErrorState with statusCode, type, and copyable details (Phase 4) ...

- Add error prop to AppErrorState accepting normalized client error object
- Show type, statusCode, and errorAlias as inline badges
- Add GnCopyButton to copy JSON-serialized error details to clipboard
- displayMessage falls back to error.message when message prop is omitted
- Update all call sites to pass full error object instead of only .message
- Add tests for error badges, copy button visibility, and clipboard content

Add toast notifications for mutations (Phase 3) ...

- Wrap RouterView in GnToastProvider in App.vue
- Replace inline rebootError alert in DeviceDetailPage with toast
- Replace inline resultAlert in ScriptDetailPage and ScriptsActionsPage with toast
- Add success toasts after successful edit, assign, remove, rename, create, setup
- Keep inline GnAlert inside modals for form-level errors

Add global error handling (Phase 2) ...

- Create useGlobalErrorHandler composable that wires up three
  global error-catching surfaces:
    1. app.config.errorHandler — Vue runtime errors (render,
       watchers, lifecycle hooks, event handlers).
    2. window 'unhandledrejection' — rejected promises without catch.
    3. window 'error' — synchronous JS runtime errors.
- Create AppErrorBoundary component wrapping RouterView to catch
  Vue errors in child components and show fallback UI (AppErrorState
  with Retry) instead of a blank screen.
- Apply the boundary in App.vue so every routed page is protected.

All 126 Vitest tests pass.

Fix critical error handling gaps in page mutations ...

- AreaDetailPage: submitRemove now checks result.ok before redirecting;
  replace GnConfirmDialog with GnModal to display remove errors inline.
- DeviceDetailPage: submitRemove now checks result.ok before redirecting;
  replace GnConfirmDialog with GnModal. reboot() now awaits and shows
  error via inline GnAlert instead of silently failing.
- ScriptDetailPage: toggleState now checks result.ok and shows success/
  danger resultAlert feedback instead of ignoring API errors.

All 126 Vitest tests pass.

Add AreaFavoriteButton component and replace star icons with bookmarks ...

- Create reusable AreaFavoriteButton component (btn-icon, bookmark-simple/fill)
- Replace inline bookmark buttons in AreaTreeNode and AreaFavoritesPage
- Use bookmark icons (ph-bookmark-simple, ph-fill) across favorites feature
- Add @phosphor-icons/web/fill import in main.js
- Update AreaTreeNode test to target new component
- Replace ph-star with ph-bookmarks in AppShell navigation
- Adjust active favorite color from danger to warning
- Remove obsolete .area-favorite-remove styles

Replace star icons with bookmark icons for favorites feature

AreaFavoritesPage: use ph-x icon for remove button with neutral base + danger hover

AreaFavoritesPage: use filled star icon to indicate already-favorite state

Fix AreaFavoritesPage: restore onMounted loadAreas for direct page refresh

Redesign AreaFavoritesPage with clickable cards, parent links, star icon button

Widen .page container from 1120px to 1200px

Fix ScriptsRegularPage: remove unused useRouter call

Hide page-header ::after pseudo-element entirely

Hide page-header hover ::after pseudo-element entirely

Disable page-header hover animation (::after)

Disable page-header animation to fix overflow:visible interaction

PageActionsDropdown: enlarge trigger button to 44x44px / 24px icon

PageActionsDropdown: use ph class instead of ph-bold for icon