fix: correct tojson|safe usage in templates and update validator

- Remove |safe from |tojson in HTML attributes (x-data) - quotes must
  become " for browsers to parse correctly
- Update LANG-002 and LANG-003 architecture rules to document correct
  |tojson usage patterns:
  - HTML attributes: |tojson (no |safe)
  - Script blocks: |tojson|safe
- Fix validator to warn when |tojson|safe is used in x-data (breaks
  HTML attribute parsing)
- Improve code quality across services, APIs, and tests

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/templates/shared/macros/language_selector.html

@@ -58,7 +58,7 @@
 {% set positions = {'left': 'left-0', 'right': 'right-0'} %}
 {# Uses languageSelector() function per LANG-002 architecture rule #}
 <div
-    x-data="languageSelector('{{ current }}', {{ langs | tojson | safe }})"
+    x-data="languageSelector('{{ current }}', {{ langs | tojson }})"
     class="relative inline-block"
 >
     <button
@@ -121,7 +121,7 @@
 {% set positions = {'left': 'left-0', 'right': 'right-0'} %}
 {# Uses languageSelector() function per LANG-002 architecture rule #}
 <div
-    x-data="languageSelector('{{ current }}', {{ langs | tojson | safe }})"
+    x-data="languageSelector('{{ current }}', {{ langs | tojson }})"
     class="relative"
 >
     <button
@@ -179,7 +179,7 @@
 {% set current = current_language if current_language in langs else langs[0] %}
 {# Uses languageSelector() function per LANG-002 architecture rule #}
 <div
-    x-data="languageSelector('{{ current }}', {{ langs | tojson | safe }})"
+    x-data="languageSelector('{{ current }}', {{ langs | tojson }})"
     class="inline-flex items-center gap-1 p-1 bg-gray-100 dark:bg-gray-700 rounded-lg"
 >
     <template x-for="lang in languages" :key="lang">