#19 — POIs tab: icon picker

[bobinush]

Icons are PNG files served from /icons/. There are approximately 80 available
but typically only 15–20 are actively used.

Acceptance criteria:

• "Browse Icons" opens a modal with a scrollable grid of all available icons
• Each cell shows the PNG image and the icon name below it
• A search input at the top of the modal filters the grid in real time by name
• Clicking an icon selects it, highlights the cell, closes the modal and shows a preview of the selected icon next to the Browse button
• The icon name is stored as a string (e.g. toilet) — the full path /icons/toilet.png is resolved at render time
• The available icon list is defined as a single array constant — easy to extend without changing any other code