Fix Merge member action in members page

[joanagmaia]

Changes proposed ✍️

What

🤖 Generated by Copilot at a20013f

Added a feature to merge members from the member-view-header.vue component and cleaned up some unused or redundant code.
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🤖 Generated by Copilot at a20013f

We're sailing on the Vue seas, me hearties
We're formatting and importing with care
We're merging members with a merge event
And we're opening a dialog in the air

Why

How

🤖 Generated by Copilot at a20013f

• Emit and handle merge event to open merge dialog for members (link, link)
• Add and render app-member-merge-dialog component to merge members (link, link, link)
• Remove unused import of AppMemberMergeDialog from member-dropdown.vue (link)

Checklist ✅

• Label appropriately with Feature, Improvement, or Bug.
• Add screehshots to the PR description for relevant FE changes
• New backend functionality has been unit-tested.
• API documentation has been updated (if necessary) (see docs on API documentation).
• Quality standards are met.