Tighten item icon viewBoxes so art fills the slot

Each icon's viewBox is set to a square box around its actual content
(with a stroke-width margin + small breathing room), leaving the path
data unchanged. Under-filled icons (ingots, plates, silicon, etc.) now
scale up and recenter to fill the half-tile item slot; already-full
icons are left as-is (clamped to only ever zoom in). Fixes items looking
too small in the game world.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Y7N59FsLA5e2kuVdqe4Uhc

bin/app/data/icons/items/dreadnought_hull.svg

@@ -1,4 +1,4 @@
-<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="100" height="100">
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="7.1 7.1 85.9 85.9" width="100" height="100">
   <path d="M50 12 L72 42 L86 80 L62 72 L58 88 L42 88 L38 72 L14 80 L28 42 Z" fill="#9fb3c9" stroke="#232a33" stroke-width="4" stroke-linejoin="round"/>
   <circle cx="50" cy="42" r="7.5" fill="#ff5533" stroke="#232a33" stroke-width="2.5"/>
   <g fill="#3a4450"><circle cx="42" cy="82" r="3.4"/><circle cx="50" cy="84" r="3.4"/><circle cx="58" cy="82" r="3.4"/></g>