feat: implement version update checker

[AjdinDev]

Adds an admin dashboard update check using the existing release-time config('app.version') value as the installed panel version.

• compares config('app.version') against the latest GitHub release tag
• treats canary as an explicit non-comparable development/source build state
• caches upstream release checks to avoid calling GitHub on every dashboard load
• shows update status in the admin overview UI
• various logic added to handle github's 67% uptime

[ericwang401]

Thanks for the pull request! I have some suggestions:

1. Please increase the data density on the UI. The version checker card and the statistic cards below are all very massive. If you can elegantly increase the data density, that would be great.
2. The "Check again" button could be positioned bottom right
3. Instead of telling the version in a sentence, we can use labels, badges, etc.

Also, if you are vibe coding this, make sure you are using an intelligent model like GPT-5.4/5.5 or Claude Sonnet/Opus. Code quality is as important as the feature itself, and I refactored your last pull request with Claude Opus.

Thanks for the hard work!

[AjdinDev]

Incorporated the requested feedback and improved some various minor things