fix(frontend): restore Android-compatible remote asset

[hotzenplotz5]

Summary

• replace the nested JPEG-in-SVG remote asset with a fully self-contained SVG rendering
• preserve the current 360x1220 geometry, 35 functional hotspots, narrow mobile width and vertical scrolling
• retain layered shell gradients, highlights, texture, key bevels and raised shadows without external or embedded raster subresources
• add a frontend contract guard that rejects <image>, data:image/* and feDropShadow in the remote asset

Root cause

PR #110 wrapped a JPEG data URI inside an SVG <image> element. Microsoft Edge on Android loaded the outer SVG but rejected the nested raster image, producing a large broken-image placeholder in the remote dialog.

Validation

• SVG parsed successfully as XML
• SVG rendered successfully to a 540x1830 PNG with Inkscape
• stored branch content verified through GitHub
• existing remote runtime test now checks that the asset is self-contained

Mobile acceptance

Install this branch with make install-runtime, restart the daemon and verify the remote in Microsoft Edge on Android. Keep this PR Draft until that real-device check passes.