Add Xquik social data skill

[kriptoburak]

Summary

• Add a Community skill for Xquik social data workflows.
• Include Zo display metadata with the required XQUIK_API_KEY secret declaration.
• Cover public REST and MCP entry points from Xquik source-truth metadata.

Validation

• bun validate exits 0. It reports existing External skill warnings unrelated to this new Community skill.
• jq parses the new DISPLAY.json.
• Public link checks pass for Xquik docs, API root, repository, and agent skills index.
• Duplicate checks pass across zocomputer/skills default tree, open and closed PRs, and open and closed issues.
• Whitespace, dash, and public diff scans pass.

[kriptoburak]

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