Add a Font Awesome icon gallery to the properties panel, draggable onto the screen

New "Icône" widget (<i class="...">, color/size customizable exactly like any other widget) plus a curated set of ~250 verified Font Awesome 5 Free solid icon names (fontawesome_icons.py) — not the full ~1500-icon catalog, since an embedded list needs to be guaranteed accurate (a wrong class name silently renders as a blank glyph); any other valid FA5 class still works by typing it directly into the widget's "Icône" setting.

The gallery lives in the (now always-visible) top of the right floating panel, searchable, with each tile both clickable and HTML5-draggable onto the canvas — either action posts to element_add with the chosen icon_class, which now seeds the new element's class instead of leaving it on the generic default. Available in the element-type template editor too, since it reuses screen_edit.html.

Loads Font Awesome 5.15.4 (cdnjs) alongside the existing animate.css/Bulma links, in both the editor and /play.

Verified end to end: gallery renders with real icon glyphs, clicking/simulated-drop creates a correctly-classed <i> element, and the actual /play route renders it with Font Awesome loaded. Full suite green (89).

routes/screens/screen_edit.py

@@ -73,4 +73,5 @@ def screen_edit(slug, screen_id):
         animation_clips=animation_clips, animation_clips_json=json.dumps(animation_clips),
         animate_css_catalog=screens.ANIMATE_CSS_CATALOG,
         animate_css_labels_json=json.dumps(screens.ANIMATE_CSS_LABELS),
+        fontawesome_icons=screens.FONTAWESOME_ICONS,
     )