Switch icons from a webfont to self-hosted SVG masks — the webfont was the actual problem

Self-hosting Font Awesome's font files (previous commit) didn't fix it either: every icon in the picker still failed identically. That rules out CDN/network blocking specifically and points to something in the browser blocking custom webfont loading altogether regardless of origin (common with strict anti-fingerprinting protection, e.g. Brave's font blocking or certain privacy extensions — @font-face loading is a well-known fingerprinting vector).

Replaced the whole mechanism: each of the 258 curated icons is now a real downloaded SVG file (static/icons/*.svg, sourced from Font Awesome 5 Free's official SVG package) displayed via CSS mask-image (.icon-svg in style.css) instead of a font glyph. A masked SVG isn't a font resource at all, so it isn't subject to webfont-blocking — and it still colors via the existing "color" style property (background-color:currentColor) and sizes via font-size (1em), so no change to how the widget's other controls work.

The "Icône" widget now stores just the icon's slug (e.g. "trophy") in a dedicated attribute instead of a full CSS class string, rendered by a new special_render (render_icone.py). Updated the add-gallery and the properties-panel picker modal to use the same mask technique for their previews, and element_add.py to validate the slug against the curated list. Removed the now-unused self-hosted Font Awesome CSS/webfont files and the <link> tags — no font dependency left for icons at all.

Verified end to end (gallery renders with real SVG previews, simulated add creates a correctly-attributed element, the SVG file is actually served, the per-element picker reflects the current icon). Full suite green (89).

static/icons/film.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512"><!-- Font Awesome Free 5.15.4 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) --><path d="M488 64h-8v20c0 6.6-5.4 12-12 12h-40c-6.6 0-12-5.4-12-12V64H96v20c0 6.6-5.4 12-12 12H44c-6.6 0-12-5.4-12-12V64h-8C10.7 64 0 74.7 0 88v336c0 13.3 10.7 24 24 24h8v-20c0-6.6 5.4-12 12-12h40c6.6 0 12 5.4 12 12v20h320v-20c0-6.6 5.4-12 12-12h40c6.6 0 12 5.4 12 12v20h8c13.3 0 24-10.7 24-24V88c0-13.3-10.7-24-24-24zM96 372c0 6.6-5.4 12-12 12H44c-6.6 0-12-5.4-12-12v-40c0-6.6 5.4-12 12-12h40c6.6 0 12 5.4 12 12v40zm0-96c0 6.6-5.4 12-12 12H44c-6.6 0-12-5.4-12-12v-40c0-6.6 5.4-12 12-12h40c6.6 0 12 5.4 12 12v40zm0-96c0 6.6-5.4 12-12 12H44c-6.6 0-12-5.4-12-12v-40c0-6.6 5.4-12 12-12h40c6.6 0 12 5.4 12 12v40zm272 208c0 6.6-5.4 12-12 12H156c-6.6 0-12-5.4-12-12v-96c0-6.6 5.4-12 12-12h200c6.6 0 12 5.4 12 12v96zm0-168c0 6.6-5.4 12-12 12H156c-6.6 0-12-5.4-12-12v-96c0-6.6 5.4-12 12-12h200c6.6 0 12 5.4 12 12v96zm112 152c0 6.6-5.4 12-12 12h-40c-6.6 0-12-5.4-12-12v-40c0-6.6 5.4-12 12-12h40c6.6 0 12 5.4 12 12v40zm0-96c0 6.6-5.4 12-12 12h-40c-6.6 0-12-5.4-12-12v-40c0-6.6 5.4-12 12-12h40c6.6 0 12 5.4 12 12v40zm0-96c0 6.6-5.4 12-12 12h-40c-6.6 0-12-5.4-12-12v-40c0-6.6 5.4-12 12-12h40c6.6 0 12 5.4 12 12v40z"/></svg>