💄 Replace language toggle with dropdown menu

Convert binary language toggle button to a dropdown menu for better
scalability. The dropdown displays the current language code (EN/FR)
and shows full language names in the menu (English/Français).

This prepares the UI for adding additional languages beyond the current
English and French support.

Changes:
- Replace Button with Dropdown component in LanguageSwitcher
- Update translation structure from "switchTo" to "languages" object
- Show active language with highlighted menu item
- Maintain localStorage persistence for language selection

Author: AndreMiras

public/locales/en/header.json

@@ -1,6 +1,9 @@
 {
   "about": "About",
   "languageSwitcher": {
-    "switchTo": "FR"
+    "languages": {
+      "en": "English",
+      "fr": "Français"
+    }
   }
 }

public/locales/fr/header.json

@@ -1,6 +1,9 @@
 {
   "about": "À propos",
   "languageSwitcher": {
-    "switchTo": "EN"
+    "languages": {
+      "en": "English",
+      "fr": "Français"
+    }
   }
 }

src/components/LanguageSwitcher.tsx

@@ -1,26 +1,35 @@
-import { Button } from "react-bootstrap";
+import { Dropdown } from "react-bootstrap";
 import { useTranslation } from "react-i18next";
 
 const LOCALE_STORAGE_KEY = "edilkamin-locale";
 
 const LanguageSwitcher = () => {
   const { t, i18n } = useTranslation("header");
 
-  const switchLanguage = () => {
-    const newLocale = i18n.language === "en" ? "fr" : "en";
-    i18n.changeLanguage(newLocale);
-    localStorage.setItem(LOCALE_STORAGE_KEY, newLocale);
+  const languages = ["en", "fr"];
+
+  const switchLanguage = (locale: string) => {
+    i18n.changeLanguage(locale);
+    localStorage.setItem(LOCALE_STORAGE_KEY, locale);
   };
 
   return (
-    <Button
-      variant="outline-light"
-      size="sm"
-      onClick={switchLanguage}
-      className="ms-2"
-    >
-      {t("languageSwitcher.switchTo")}
-    </Button>
+    <Dropdown className="ms-2">
+      <Dropdown.Toggle variant="outline-secondary">
+        {i18n.language.toUpperCase()}
+      </Dropdown.Toggle>
+      <Dropdown.Menu>
+        {languages.map((locale) => (
+          <Dropdown.Item
+            key={locale}
+            active={i18n.language === locale}
+            onClick={() => switchLanguage(locale)}
+          >
+            {t(`languageSwitcher.languages.${locale}`)}
+          </Dropdown.Item>
+        ))}
+      </Dropdown.Menu>
+    </Dropdown>
   );
 };