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/salvager_module.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="10.8 9.3 78.4 78.4" width="100" height="100">
   <circle cx="50" cy="28" r="13" fill="#b2cfdd" stroke="#1c4a30" stroke-width="3.5"/>
   <circle cx="50" cy="28" r="5" fill="#5f8f78"/>
   <path d="M50 41 L50 56" stroke="#1c4a30" stroke-width="5" stroke-linecap="round"/>