feat(tasks): persist view mode and support ?view=kanban URL parameter

View mode (list/kanban) is now saved to localStorage and restored on
page load. URL parameter ?view=kanban takes precedence, enabling tablet
kiosk setups to default to Kanban view. Toggle buttons reflect the
active view correctly on initial render.

Closes #17

package.json

@@ -1,6 +1,6 @@
 {
   "name": "oikos",
-  "version": "0.9.0",
+  "version": "0.9.1",
   "description": "Self-hosted family planner - calendar, tasks, shopping, meal planning, budget and more. Private, open-source, no subscription.",
   "main": "server/index.js",
   "type": "module",