SimCity-style toolbar: colored pictogram icons + grouped UX

- All 16 icons redrawn as rich multi-color SVGs (houses, towers,
  factory, plants with smoke, services with badges/crosses, park,
  fountain, stadium) — unique gradient ids, no collisions
- Toolbar grouped under labeled sections: Tools / Zones / Power /
  Safety / Health / Leisure
- Every button shows price (FREE for zones); unaffordable buildings
  dim and turn red as funds change
- Keyboard-shortcut badges on buttons; bigger 30px icons; hover lift
- Floating status chip above the bar shows active tool, price,
  upkeep and coverage radius (SimCity status-bar feel)
- FIX: Game.ui was a method while input.js read it as a property, so
  tool-change UI updates silently never ran; now a proper getter

src/main.js

@@ -101,16 +101,16 @@ class Game {
     this.speedIdx = 1;
     this.paused = false;
     this.start(c);
-    this.ui().toast(`Welcome to ${name}, Mayor!`, 'success');
-    this.ui().resetQuests();
+    this.ui?.toast(`Welcome to ${name}, Mayor!`, 'success');
+    this.ui?.resetQuests();
   }
 
   loadFrom(cityInstance) {
     this.start(cityInstance);
-    this.ui().toast('City loaded.', 'success');
+    this.ui?.toast('City loaded.', 'success');
   }
 
-  ui() { return this._parts?.ui; }
+  get ui() { return this._parts?.ui; }
   get input() { return this._parts?.input; }
   get renderer() { return this._parts?.renderer; }
 
@@ -120,7 +120,7 @@ class Game {
     this.speedIdx = idx;
     this.paused = idx === 0;
     if (idx > 0) this.lastNonzeroSpeed = idx;
-    this.ui()?.setSpeedActive(idx);
+    this.ui?.setSpeedActive(idx);
   }
 
   togglePause() {
@@ -137,16 +137,16 @@ class Game {
 
   queryTile(tile, x, y) {
     const info = this.city.getTileInfo(tile.x, tile.z);
-    if (info) this.ui()?.showInfoPopup(info, x, y);
+    if (info) this.ui?.showInfoPopup(info, x, y);
   }
 
-  checkQuests() { this.ui()?.checkQuests(); }
+  checkQuests() { this.ui?.checkQuests(); }
 
   _syncSoon() {
     if (this.city.tilesDirty && this._parts) {
       this._parts.renderer.sync();
       this.city.tilesDirty = false;
-      this.ui()?.scheduleMinimap();
+      this.ui?.scheduleMinimap();
     }
   }