feat: Appwrite client exponential backoff connection retries (#678)

[knoxiboy]

Description

Resolves #678

This PR implements Appwrite client initialization reconnection logic using an exponential backoff retry loop. A floating, real-time reconnection status banner is added to notify users of retry progress and connection status.

What changed

• Replaced the direct connection logic in CloudSync.init() with CloudSync.initWithBackoff(attempt).
• Implemented exponential backoff delays based on Math.min(30000, Math.pow(2, attempt) * 1000).
• Added floating reconnection banner UI helpers showReconnectionBanner and hideReconnectionBanner to display status and current retry countdowns.
• Automatic flushing of offline-queued writes on successful reconnection.

Why

When the Appwrite service or network is offline, direct client initialization throws an uncaught error and fails silently. This prevents the application from attempting to sync once network connectivity or service is restored.

How to test

1. Modify .env or temporarily disconnect internet access.
2. Load the application and verify that the floating "Appwrite Connection Offline" banner is rendered at the bottom right.
3. Verify that it retries with an increasing exponential backoff delay (2s, 4s, 8s, 16s, up to 30s).
4. Restore connectivity and verify that the banner automatically hides once a connection is successfully established.

Checklist

• Tested changes locally
• No lint/syntax errors introduced
• Matches all issue criteria

Files Affected

• src/cloud-sync.js

[knoxiboy]

@Shruti070107 Please review this pr and merge it

[knoxiboy]

@Shruti070107 Please review this pr and merge it