feat: Ukrainian translation, UAH currency, shopping category i18n (closes #52)

- Add Ukrainian (uk) locale to SUPPORTED_LOCALES and locale picker
- Add public/locales/uk.json (622 keys, full Ukrainian translation)
- Add UAH (Ukrainian Hryvnia) to SUPPORTED_CURRENCIES and VALID_CURRENCIES
- Add CATEGORY_I18N map and catLabel() in settings.js to translate default
  shopping category names in the settings panel; rename and delete dialogs
  now also use the translated name instead of the raw German DB string
- Align server VALID_CURRENCIES with frontend: add missing AED, BRL, INR, SAR

Co-Authored-By: baragoon <baragoon@users.noreply.github.com>
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "oikos",
-  "version": "0.20.8",
+  "version": "0.20.9",
   "description": "Self-hosted family planner - calendar, tasks, shopping, meal planning, budget and more. Private, open-source, no subscription.",
   "main": "server/index.js",
   "type": "module",