feat(dashboard): Link the restore doc in the archived site banner (backport #7423)

[mergify]

Problem

The Backups tab of an archived site shows a banner. The banner says only
"Need help with restoring your archived site." and gives a Contact Support
button. The user cannot see that they can do the restore themselves.

Change

The banner now points to the documentation that gives the steps:

To restore an archived site backup, follow the documentation. If you need more assistance, contact support.

The Contact Support button is removed. The text contains a link to
support.frappe.io in its place. The dismiss button does not change, and the
banner still shows only when the site is archived and it has backups.

AlertBanner puts the title into the page with v-html, so the links show
correctly. The link markup is the same as the markup in the shared bench
upsell banner in the same file.

Test

• The documentation URL gives HTTP 200 and the page contains the
  restore-archived-site anchor. support.frappe.io gives HTTP 200.
• Checked in a local dashboard on an archived site that has backups. The
  banner shows the new text, both links work, and the button is gone.
• Biome reports no problem in the changed file.

  ---

  This is an automatic backport of pull request feat(dashboard): Link the restore doc in the archived site banner #7423 done by Mergify.

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.89%. Comparing base (d17d9d0) to head (a2c9f33).
⚠️ Report is 8 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #7439       +/-   ##
===========================================
+ Coverage   61.27%   86.89%   +25.62%     
===========================================
  Files        1042      137      -905     
  Lines       99787    26322    -73465     
  Branches     1707     1707               
===========================================
- Hits        61144    22873    -38271     
+ Misses      38602     3408    -35194     
  Partials       41       41               

Flag	Coverage Δ
dashboard	86.89% <100.00%> (-0.02%)	⬇️

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