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/clipboard-list.svg

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+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 384 512"><!-- 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="M336 64h-80c0-35.3-28.7-64-64-64s-64 28.7-64 64H48C21.5 64 0 85.5 0 112v352c0 26.5 21.5 48 48 48h288c26.5 0 48-21.5 48-48V112c0-26.5-21.5-48-48-48zM96 424c-13.3 0-24-10.7-24-24s10.7-24 24-24 24 10.7 24 24-10.7 24-24 24zm0-96c-13.3 0-24-10.7-24-24s10.7-24 24-24 24 10.7 24 24-10.7 24-24 24zm0-96c-13.3 0-24-10.7-24-24s10.7-24 24-24 24 10.7 24 24-10.7 24-24 24zm96-192c13.3 0 24 10.7 24 24s-10.7 24-24 24-24-10.7-24-24 10.7-24 24-24zm128 368c0 4.4-3.6 8-8 8H168c-4.4 0-8-3.6-8-8v-16c0-4.4 3.6-8 8-8h144c4.4 0 8 3.6 8 8v16zm0-96c0 4.4-3.6 8-8 8H168c-4.4 0-8-3.6-8-8v-16c0-4.4 3.6-8 8-8h144c4.4 0 8 3.6 8 8v16zm0-96c0 4.4-3.6 8-8 8H168c-4.4 0-8-3.6-8-8v-16c0-4.4 3.6-8 8-8h144c4.4 0 8 3.6 8 8v16z"/></svg>