Prepare PlotMapper v1.3.0 release

[maxliebscher]

Summary

• prepares PlotMapper v1.3.0 release assets, notes, standalone HTML, and README screenshot gallery
• fixes README German encoding, project-menu map-load icon consistency, CRLF help-copy check, and presentation PNG export parity
• updates smoke coverage for presentation PNG Sichtfeld export

Verification

• npm.cmd test
• npm.cmd run smoke
• npm.cmd run build
• git diff --check
• README image link check: 10/10 local assets present

Release assets

• releases/Plotmapper_v1.3.0.md
• releases/Plotmapper_v1.3.0.html
• releases/v1.3.0.jpg