perf(core): read the user status from initial state

[pringelmann]

Summary

user_status already puts the current status into every logged-in page's initial state, but AccountMenu.vue refetched it over OCS in created(). Reading the initial state instead saves a request and a duplicate query per page load, and the badge is there on first paint.

Also drops the :key hack on NcAvatar, which only existed because the status used to arrive late.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes: no visual change
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI (tests, reviewed)

[pringelmann]

/backport to stable35