Redesign the interface as a hand-made dev zine

Replaces the gradient, frosted-glass look with flat warm ink, hard
black edges and offset shadows, a clashing lime/pink/sky/tangerine
palette, and self-hosted Archivo Black, Atkinson Hyperlegible and Space
Mono (Inter is gone). Stickers, slight tilts, a marker-style heading,
a barber-pole progress bar, wiggling icons and chattier copy give it
some restless energy; reduced-motion users get none of the animation.

Toolbar buttons are now labelled chips in consistent groups (Open;
2D/3D/City; Fit/Layers/Code/palette; Lines/Refs), and the city bar is
one even row: Heli, Walk, Fly, then Tour and Copy link with shortcuts,
help text underneath and the address moved to the top right. Copy link
feedback no longer wipes the button's icon.

A tab half way down the sidebar's left edge (or [) folds the sidebar
away and back, remembered per device. The local folder option is
hidden unless the server reports it enabled. Canvas text, posters and
signs switch to the new fonts once loaded, and the city's ground, fog,
grid, pavements and wall are warmed to match.

web/favicon.svg

@@ -1,6 +1,8 @@
 <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 64 64">
-  <rect width="64" height="64" rx="14" fill="#171918"/>
-  <path d="M10 13h44v38H10z" fill="#202b28" stroke="#65b3ff" stroke-width="3"/>
-  <path d="M10 29h44M29 13v38M29 40h25" fill="none" stroke="#29c997" stroke-width="3"/>
-  <path d="M15 19h9M15 23h7M34 19h14M34 23h10M15 35h9M15 39h7M34 46h13" fill="none" stroke="#d6dad7" stroke-linecap="round" stroke-width="2" opacity=".82"/>
+  <rect width="64" height="64" rx="12" fill="#1e1b16"/>
+  <g stroke="#000" stroke-width="3" transform="rotate(-6 32 32)">
+    <rect x="8" y="24" width="15" height="32" rx="2" fill="#c8f135"/>
+    <rect x="25" y="8" width="15" height="48" rx="2" fill="#ff5ea8"/>
+    <rect x="42" y="32" width="15" height="24" rx="2" fill="#5cc8ff"/>
+  </g>
 </svg>