Fix/resolve svg issues on artemis

[FadyGergesRezk]

Checklist

• I linked PR with a related issue
• I added multiple screenshots/screencasts of my UI changes

Motivation and Context

We need SVG exports that work in both web environments (theme-adaptive) and non-CSS renderers (PowerPoint/Inkscape). The prior export path flattened CSS variables unconditionally, breaking dark/light mode in the web, while compat output must stay stable for PPT/Inkscape.

Description

• Added two SVG export modes:
  • Web SVG (default) keeps CSS variables and includes :root fallbacks so it adapts to theme in browsers.
  • Compat SVG resolves CSS variables to fallback values and inlines attributes for PowerPoint/Inkscape.
• Added a new export option in the web app: "As SVG (PowerPoint/Inkscape)".
• Export pipeline now selects behavior via svgMode in ExportOptions.
• Compat export uses the original fallback palette (light) regardless of current theme, preserving the old Inkscape/PPT behavior.
• Aligned label placement for SFC Transition Branch, PetriNet Place, and PetriNet Transition to the Use Case actor pattern by extending the SVG height with a dedicated label band and centering the label inside it; adjusted sidebar preview height to avoid overlap.

Steps for Testing

1. Run the web app, switch between light/dark theme.
2. Export As SVG and open the file in a browser: colors should follow the current theme.
3. Export As SVG (PowerPoint/Inkscape) and open in Inkscape or PowerPoint: colors should be stable (light) and connectors visible.
4. In the sidebar, verify PetriNet and SFC elements no longer overlap and labels render cleanly.

Screenshots

N/A (no UI screenshots yet)