fix: Alpine.js JSON parsing error in x-data HTML attributes

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>

client/templates/measure/select_recipe.html

@@ -4,7 +4,7 @@
 {% block content %}
 <div class="container mx-auto px-4 sm:px-6 lg:px-8 py-8 max-w-7xl"
      x-data="{
-       recipes: {{ recipes|tojson }},
+       recipes: {{ recipes|tojson_attr }},
        search: '{{ auto_recipe_code }}',
        lot_number: '{{ auto_lot }}',
        serial_number: '{{ auto_serial }}',