feat: complete UI/UX overhaul - dashboard unification, calendar UX, mobile optimization

- Dashboard redesign as command center with filters, quick actions, inline approve/reject
- Reusable components: BookingRow, BookingFilters, ActionMenu, BookingPreviewModal, BookingEditModal
- Calendar: drag & drop reschedule, eventClick preview modal, grid/list toggle
- Mobile: segmented control bookings/calendar toggle, compact pills, responsive layout
- Collapsible filters with active count badge
- Smart menu positioning with Teleport
- Calendar/list bidirectional data sync
- Navigation: unified History page, removed AdminPending
- Google Calendar OAuth integration
- Dark mode contrast improvements, breadcrumb navigation
- useLocalStorage composable for state persistence

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/services/booking_service.py

@@ -93,10 +93,11 @@ def validate_booking_rules(
             f"Rezervările sunt permise doar între {wh_start}:00 și {wh_end}:00"
         )
 
-    # c) Check for overlapping bookings
+    # c) Check for overlapping bookings (only approved block new bookings;
+    #    admin re-validates at approval time to catch conflicts)
     query = db.query(Booking).filter(
         Booking.space_id == space_id,
-        Booking.status.in_(["approved", "pending"]),
+        Booking.status == "approved",
         and_(
             Booking.start_datetime < end_datetime,
             Booking.end_datetime > start_datetime,