Add runtime resource loading and fix Docker incremental builds

- Build images.tar.gz bitmap archive for KiCad icons
- Fetch resources at runtime via HTTP instead of bundling in WASM
- Write to Emscripten virtual FS at compile-time KICAD_DATA path
- Fix rsync timestamp handling for correct make change detection
- Update kicad submodule with WASM settings manager fix

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitignore

@@ -47,6 +47,7 @@ wxwidgets-clean/
 /tests/apps/standalone/*/*.wasm
 /tests/apps/kicad/*.js
 /tests/apps/kicad/*.wasm
+/tests/apps/kicad/*.tar.gz
 !tests/apps/kicad/pcbnew.html
 /temp/
 *.log