feat: out-of-order webhook delivery guard

[Flo4604]

Summary

• Adds a timestamp guard in the deploy workflow's auto-promote logic to prevent older git commits from overtaking newer ones when webhooks arrive out of order
• Only compares timestamps when both the new and current live deployment have valid git commit timestamps (git-sourced deployments)
• CLI/docker uploads (no timestamp) skip the guard entirely and auto-promote as before

Test plan

• Deploy commit A (timestamp 100), verify it auto-promotes
• Deploy commit B (timestamp 200), verify it auto-promotes (newer)
• Deploy commit C (timestamp 50), verify it does NOT auto-promote (older than live)
• Deploy via CLI (no timestamp), verify auto-promote still works

Stack: 1/3

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Project	Deployment	Actions	Updated (UTC)
dashboard	Ready	Preview, Comment	Feb 20, 2026 0:22am
engineering	Ready	Preview, Comment	Feb 20, 2026 0:22am

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[Flo4604]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat: out-of-order webhook delivery guard #5097 : 2 dependent PRs (#5098 , #5099 ) 👈 (View in Graphite)
• feat: remove legacy project columns, old settings tables, and app_id defaults #5096
• feat: app-scoped control plane for multi-app deployments #5095
• feat: add apps table and app-scoped schema for multi-app support #5094
• main

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