fix(i18n): restore pre-existing AppearanceSettings translations

Task 7 inadvertently overwrote 18 carefully-tuned translations across 7 languages
(ar/de/es/fr/ja/ko/pt) with the plan author's slightly different wording while
adding the new themeColor / zoomLevel / resetToDefaults keys. The new additions
remain intact; only the pre-existing keys are reverted to the project's original
translations (e.g. de "Designmodus" instead of "Design-Modus", ja
"システム追従" instead of "システムに従う"). Affects: sectionDescription,
themeMode, placeholder, system, currentTheme.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/i18n/messages/es.json

@@ -101,12 +101,12 @@
   "AppearanceSettings": {
     "sectionTitle": "Apariencia del tema",
     "sectionDescription": "Elige claro, oscuro o seguir el sistema. La configuración se guarda automáticamente.",
-    "themeMode": "Modo del tema",
-    "placeholder": "Selecciona el modo del tema",
+    "themeMode": "Modo de tema",
+    "placeholder": "Selecciona el modo de tema",
     "system": "Seguir el sistema",
     "light": "Claro",
     "dark": "Oscuro",
-    "currentTheme": "Tema actual: {theme}",
+    "currentTheme": "Tema efectivo actual: {theme}",
     "resolvedTheme": {
       "light": "Claro",
       "dark": "Oscuro",