feat(i18n): add French (fr) locale (#878)

Complete French translation for all 7 locale files:
auth, chat, codeEditor, common, settings, sidebar, tasks.

Also fixes a bug in languages.js where the Turkish and Italian
entries shared the same object (missing closing brace), causing
Italian to be silently dropped from the supported languages list.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

src/i18n/languages.js

@@ -14,6 +14,11 @@ export const languages = [
     label: 'English',
     nativeName: 'English',
   },
+  {
+    value: 'fr',
+    label: 'French',
+    nativeName: 'Français',
+  },
   {
     value: 'ko',
     label: 'Korean',
@@ -48,6 +53,8 @@ export const languages = [
     value: 'tr',
     label: 'Turkish',
     nativeName: 'Türkçe',
+  },
+  {
     value: 'it',
     label: 'Italian',
     nativeName: 'Italiano',