feat: enhance the global HTML structure

[tdruez]

Changes

• move the scripts out of the HTML body
• add missing DOMContentLoaded wrapper
• refactor resource viewer js into its own file
• move local app js files to js/ dir
• init resource viewer on script load
• remove dead js code
• move large js code into their own file
• remove VULNERABLECODE_URL from context_processors
• move billboard script to block extrahead
• fix the event for charts display
• move modals to a dedicated block
• do not load search_syntax_modal on all pages
• move dynamic modal js to main.js
• simplify loading overlay on form submission
• move the project_form js to its own script file
• Revert "remove the need for a base_htmx.html template"