Fix Microsoft Store appx validation: add base SmallTile/LargeTile tiles

[sejas]

Problem

Publishing Studio v1.11.0 to the Microsoft Store fails package acceptance validation for both unsigned packages (x64 + arm64):

The following image(s) specified in the appxManifest.xml … were not found: Assets\SmallTile.png, Assets\LargeTile.png

Root cause

• The appx manifest (electron2appx template) hardcodes Square71x71Logo="Assets\SmallTile.png" and Square310x310Logo="Assets\LargeTile.png".
• apps/studio/assets/appx/ shipped only scale-* variants for those two tiles — no bare SmallTile.png / LargeTile.png.
• The appx is built with makePri: false (scripts/package-appx.mjs), so there's no resources.pri to resolve a bare logical name to its scale-qualified files → Store validation can't find them.
• Tiles that pass (Square150x150Logo, Wide310x150Logo, StoreLogo) all ship a base .png. StoreLogo ships base and scale-* together and passes — proving base+scale coexistence is safe under the current build.

Fix

Add the two missing base PNGs (copies of the scale-100 variants):

File	Size	Manifest slot
SmallTile.png	71×71	Square71x71Logo
LargeTile.png	310×310	Square310x310Logo

scale-100 is exactly the canonical base size for each slot. No code or manifest changes.

Verification

• ✅ Local: both files present, dimensions confirmed (71×71, 310×310).
• ✅ Manifest references (Assets\SmallTile.png, Assets\LargeTile.png) now have matching files.
• ⏳ Real validation needs a Windows appx rebuild (scripts/package-appx.mjs) — unzip the produced .appx, confirm Assets/SmallTile.png + Assets/LargeTile.png exist, re-run Microsoft Store package acceptance (x64 + arm64).

Fixes STU-1837

🤖 Generated with Claude Code

[sejas]

I triggered the appx builds and confirmed they worked as expected in the MS Store. We can upload the next version as we normally do.