feat: add client-side permission gating to all write-action UIs

Gate all mutating UI elements with useCanDo() permission checks:
- BudgetPanel (budget_edit), PackingListPanel (packing_edit)
- DayPlanSidebar, DayDetailPanel (day_edit)
- ReservationsPanel, ReservationModal (reservation_edit)
- CollabNotes, CollabPolls, CollabChat (collab_edit)
- FileManager (file_edit, file_delete, file_upload)
- PlaceFormModal, PlaceInspector, PlacesSidebar (place_edit, file_upload)
- TripFormModal (trip_edit, trip_cover_upload)
- DashboardPage (trip_edit, trip_cover_upload, trip_delete, trip_archive)
- TripMembersModal (member_manage, share_manage)

Also: fix redundant getTripOwnerId queries in trips.ts, remove dead
getTripOwnerId function, fix TripMembersModal grid when share hidden,
fix canRemove logic, guard TripListItem empty actions div.

client/src/components/Planner/PlacesSidebar.tsx

@@ -229,9 +229,9 @@ const PlacesSidebar = React.memo(function PlacesSidebar({
             <span style={{ fontSize: 13, color: 'var(--text-faint)' }}>
               {filter === 'unplanned' ? t('places.allPlanned') : t('places.noneFound')}
             </span>
-            <button onClick={onAddPlace} style={{ fontSize: 12, color: 'var(--text-primary)', background: 'none', border: 'none', cursor: 'pointer', textDecoration: 'underline', fontFamily: 'inherit' }}>
+            {canEditPlaces && <button onClick={onAddPlace} style={{ fontSize: 12, color: 'var(--text-primary)', background: 'none', border: 'none', cursor: 'pointer', textDecoration: 'underline', fontFamily: 'inherit' }}>
               {t('places.addPlace')}
-            </button>
+            </button>}
           </div>
         ) : (
           filtered.map(place => {