Add tojson_attr Jinja2 filter that escapes double quotes to "
for safe embedding in HTML attributes. The browser decodes entities
before Alpine.js evaluates, so JSON parses correctly.
Replaces |tojson with |tojson_attr in x-data attributes (select_recipe,
recipe_list, base flash messages). Script tag usages are unaffected.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>