feat: improved update notifications (backport #26314)

[mergify]

This broke since #15102

TODO:

• fix app update notifications
• Reduce frequency from daily to weekly/monhly.
• Make it work with FC (where git repo information isn't present at all)
• Point to FC dashboard
• Fetch security disclosures too?
• handle major/minor updates separately

---

This is an automatic backport of pull request #26314 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 330a1b2 has failed:

On branch mergify/bp/version-15-hotfix/pr-26314
Your branch is up to date with 'origin/version-15-hotfix'.

You are currently cherry-picking commit 330a1b2044.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   frappe/boot.py
	modified:   frappe/hooks.py
	modified:   frappe/public/js/frappe/desk.js

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   frappe/utils/change_log.py

Cherry-pick of 5ca14bb has failed:

On branch mergify/bp/version-15-hotfix/pr-26314
Your branch is ahead of 'origin/version-15-hotfix' by 2 commits.
  (use "git push" to publish your local commits)

You are currently cherry-picking commit 5ca14bb171.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   frappe/boot.py
	new file:   frappe/utils/frappecloud.py

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   frappe/tests/test_utils.py
	both modified:   frappe/utils/change_log.py
	both modified:   pyproject.toml

Cherry-pick of 45026ae has failed:

On branch mergify/bp/version-15-hotfix/pr-26314
Your branch is ahead of 'origin/version-15-hotfix' by 5 commits.
  (use "git push" to publish your local commits)

You are currently cherry-picking commit 45026aed37.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   frappe/utils/change_log.py

no changes added to commit (use "git add" and/or "git commit -a")

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[frappe-pr-bot]

🎉 This PR is included in version 15.26.0 🎉

The release is available on GitHub release

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