Refactor UptimeStatus component to improve data fetching and user experience

- Removed UpdateTimer component and integrated countdown functionality directly into UptimeStatusIsland.
- Implemented sessionStorage caching for system status data to enhance performance and user experience.
- Added visual countdown display for the next update, improving user awareness of data refresh timing.
- Updated privacy policy to clarify the use of sessionStorage for caching non-personal data.

src/components/UptimeStatus.astro

@@ -1,11 +1,8 @@
 ---
 import UptimeStatusIsland from './UptimeStatusIsland.jsx';
-import UpdateTimer from './UpdateTimer.jsx';
 ---
-<UpdateTimer client:only="react" onRefresh={() => {}} />
 <UptimeStatusIsland client:only="react" />
 
-
 <style>
 /**** Custom grid for 40 heartbeat squares ****/
 .grid-cols-40 {