Fix activities filtering (member page)

[peoray]

Changes proposed ✍️

What

Fixes #1595

🤖 Generated by Copilot at e8a0d15

Added a clear filter feature and a no activities message to the activity timeline component. This improves the user experience and functionality of the activity-timeline.vue file in the frontend module.
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🤖 Generated by Copilot at e8a0d15

platformFilter clears
activities reload anew
autumn leaves no trace

Why

How

🤖 Generated by Copilot at e8a0d15

• Add a clearable filter for platforms in the activity timeline (link)
• Show a message when there are no activities for the selected platform or member (link)
• Define a method to reload the activities without any platform filter (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.

[joanagmaia]

Looking good 😄 Just added a comment for some small copy fixes

[joanagmaia]

LGTM 🚀