Restructure assets to top-level package and add Reset Map button

- Move assets from internal/assets to top-level assets/ package for clean embed directive
- Consolidate all static files in single location (assets/static/)
- Remove duplicate static file locations to maintain single source of truth
- Add Reset Map button to map controls with full functionality
- Implement resetMap() method to return map to calculated origin position
- Store origin in this.mapOrigin for reset functionality
- Fix go:embed pattern to work without parent directory references

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

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

assets/static/aircraft-icon.svg

@@ -0,0 +1,5 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="#00a8ff" stroke="#ffffff" stroke-width="1">
+  <path d="M12 2l-2 16 2-2 2 2-2-16z"/>
+  <path d="M4 10l8-2-1 2-7 0z"/>
+  <path d="M20 10l-8-2 1 2 7 0z"/>
+</svg>