fix(modal): add fallback timer for mobile close animation

On mobile, closeModal() relies on the CSS animationend event to call
_doClose(). When the animation does not fire (prefers-reduced-motion,
tab switch, browser quirk), the modal stays stuck and the user cannot
dismiss it. A 300ms fallback timer now guarantees cleanup runs.

Reported in discussion #9

package.json

@@ -1,6 +1,6 @@
 {
   "name": "oikos",
-  "version": "0.7.6",
+  "version": "0.7.7",
   "description": "Self-hosted family planner - calendar, tasks, shopping, meal planning, budget and more. Private, open-source, no subscription.",
   "main": "server/index.js",
   "type": "module",