[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>

client/simple/tools/jinja_svg_catalog.html.edge

@@ -0,0 +1,26 @@
+{{--
+This is a EDGE https://edgejs.dev/ template to generate a HTML Jinja template
+for the backend.  Example output of this EDGE template:
+- https://github.com/searxng/searxng/blob/master/searx/templates/simple/icons.html
+--}}
+{#
+Catalog of SVG symbols that can be inserted into the HTML output of a Jinja
+template. This file from:
+
+  client/simple/tools/icon_catalog.edge.html
+#}
+
+{%-
+set catalog = {
+@each((svg, name) in svg_catalog)
+    "{{{name}}}" : """{{{svg}}}""",
+@end
+}
+-%}
+
+@each(macro in macros)
+
+{% macro {{ macro.name }}(action, alt) -%}
+  {{ open_curly_brace }} catalog[action] | replace("{{__jinja_class_placeholder__}}", "{{ macro.class }}") | safe {{ close_curly_brace }}
+{%- endmacro %}
+@end