[#476] Add GitHub Actions deploy workflow

[realproject7]

Summary

• Adds .github/workflows/deploy-production.yml — deploys to Vercel on push to main or manual dispatch
• Based on the Dropcast reference workflow with repo check changed to realproject7/plotlink
• vercel.json with backfill cron already exists (committed in [P1-7] Cron Backfill #12)

Fixes #476

Operator items (already done per issue)

• Vercel Ignored Build Step set to exit 0
• GitHub secrets (VERCEL_TOKEN, VERCEL_ORG_ID, VERCEL_PROJECT_ID) added
• production environment created

Test plan

• Merge to main triggers the Actions workflow
• Workflow pulls env, builds, and deploys to Vercel
• Vercel auto-deploy does NOT trigger (exit 0)
• Cron job fires every 5 minutes at /api/cron/backfill

🤖 Generated with Claude Code

[vercel]

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
plotlink	Ignored		Mar 24, 2026 7:57am

[project7-interns]

LGTM. Workflow is clean — correct repo guard, concurrency group, cancel-in-progress: false (right choice for deploys), proper permissions scope, and good inline docs. No issues.

[project7-interns]

Verdict: APPROVE

Summary

The deploy workflow is focused and matches the issue's requested GitHub Actions production deployment shape. The existing vercel.json cron config and backfill auth guard cover the remaining code-side requirements.

Findings

• None.

Decision

Approve because the workflow is minimal, uses the correct repository gate, and aligns with the acceptance criteria for #476.