fix: retake admin screenshots in portrait with working emoji icons

- All admin screenshots retaken at 412×892 @2.625x (pixel 9a portrait)
- Fixed emoji rendering — ni-icon emojis now show colored icons (📈⚙️👥🏢📋📤📥)
- Fixed ADMIN_GUIDE.md TOC: 'Cantaloupe Data Sync' → 'Excel Import'
- Fixed sidebar nav list: '🔄 Sync' → '📥 Import'

docs/ADMIN_GUIDE.md

@@ -10,7 +10,7 @@
 4. [Managing Users](#4-managing-users)
 5. [Geofences (Service Areas)](#5-geofences-service-areas)
 6. [Settings & Configuration](#6-settings--configuration)
-7. [Cantaloupe Data Sync](#7-cantaloupe-data-sync)
+7. [Excel Import](#7-excel-import)
 8. [Activity Log & Reports](#8-activity-log--reports)
 9. [Tips & Troubleshooting](#9-tips--troubleshooting)
 
@@ -61,7 +61,7 @@ The sidebar on the left provides access to:
 - **🏢 Customers** — Customer and location management
 - **👥 Users** — User account management
 - **📍 Geofences** — Service area polygon management
-- **🔄 Sync** — Cantaloupe data import
+- **📥 Import** — Cantaloupe Excel data import
 - **⚙️ Settings** — Categories, makes, models, key types, badge types
 - **📋 Activity** — Full activity log with filters
 - **📤 Exports** — CSV data export