feat(i18n): add Swedish (sv) translation and Italian as explicit language option (#19)

Swedish translation contributed by @olsson82 (PR #19), integrated with
minor corrections (dayShortSunday: Sun → Sön, amountLabel aligned with
v0.11.2, new v0.11.2 currency keys added).

Italian was already supported server-side but is now explicitly listed
in the locale picker alongside German, English, and Swedish.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "oikos",
-  "version": "0.11.2",
+  "version": "0.11.3",
   "description": "Self-hosted family planner - calendar, tasks, shopping, meal planning, budget and more. Private, open-source, no subscription.",
   "main": "server/index.js",
   "type": "module",