[web-client] simple theme: refactor jinja_svg_catalog and cleanup icon names

This patch implements the template generation of the template:

  searx/templates/simple/icons.html

by the way the icon set (the icon names) has been normalized:

  film-outline   --> film
  magnet-outline --> magnet
  ..
  warning        --> alert

Some missing (categorie) icons had been added.

Some of the ionicons are not suitable for a dark theme, we fixed the svg
manually in src/svg/ionicons:

- https://github.com/searxng/searxng/pull/4284#issuecomment-2680550342

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

utils/lib_sxng_vite.sh

@@ -36,6 +36,7 @@ vite.simple.build() {
         pushd "${VITE_SIMPLE_THEME}"
         npm install
         npm run fix
+        npm run icons.html
         npm run build
 
     )