New Page: "Cities"

This page allows you to:
- Index all Invaders by city.
- Display statistics per city (total score, number of invasion waves, etc.).
- Mark all Invaders in a city as flashed with one click.
- Open a city directly on the map.

Map Improvements

- Marker resizing: Option to increase or decrease the size of markers.
- Integration of off-game artworks: Display of all Invader's visible creations, but not flashable in *FlashInvaders*.

New Menu

Available on the following pages:
- Search results
- City pages
- Invader pages
- Map (in deployment)
It is located below the Invaders.
Menu Features:
- Share the SI link.
- Generate and display the SI QR code.
- Open the SI on Instagram.
- Mark the SI as flashed:
- For logged-in users: Update in the database.
- For non-logged-in users: Save in local storage.