fix: remove will-change from nav-bottom and add iOS height fallback

will-change: transform on a position:relative flex child causes iOS WebKit
to composite the element at an incorrect position - creating a visible gap
below the nav bar. Remove it; CSS transform transitions use hardware
acceleration automatically on modern iOS without this hint.

Add -webkit-fill-available before 100dvh on .app-shell as a fallback for
iOS WebKit versions where 100dvh is computed slightly smaller than the
actual WKWebView height.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "oikos",
-  "version": "0.20.4",
+  "version": "0.20.5",
   "description": "Self-hosted family planner - calendar, tasks, shopping, meal planning, budget and more. Private, open-source, no subscription.",
   "main": "server/index.js",
   "type": "module",