feat(i18n): add French language support and enhance localization

- Introduced French as a supported language across the application, updating locale files and adding translations for various components.
- Enhanced language handling logic to accommodate French, ensuring proper detection and fallback mechanisms.
- Updated UI elements to include French language options, improving accessibility for French-speaking users.
- Refactored SEO handling to include French in hreflang links, enhancing search engine indexing for multilingual content.
- Added new scripts for managing French translations and ensuring consistency across language files.

backend/migrations/20260402120000-add-ui-locale-fr-user-param-value.cjs

@@ -0,0 +1,30 @@
+'use strict';
+
+/** @type {import('sequelize-cli').Migration} */
+module.exports = {
+  async up(queryInterface) {
+    await queryInterface.sequelize.query(`
+      INSERT INTO type.user_param_value (user_param_type_id, value, order_id)
+      SELECT upt.id, 'fr', COALESCE(
+        (SELECT MAX(v.order_id) FROM type.user_param_value v WHERE v.user_param_type_id = upt.id),
+        0
+      ) + 1
+      FROM type.user_param upt
+      WHERE upt.description = 'language'
+        AND NOT EXISTS (
+          SELECT 1 FROM type.user_param_value x
+          WHERE x.user_param_type_id = upt.id AND x.value = 'fr'
+        );
+    `);
+  },
+
+  async down(queryInterface) {
+    await queryInterface.sequelize.query(`
+      DELETE FROM type.user_param_value v
+      USING type.user_param upt
+      WHERE v.user_param_type_id = upt.id
+        AND upt.description = 'language'
+        AND v.value = 'fr';
+    `);
+  },
+};