feat(fpga): Vivado cloud synthesis workflow

[gHashTag]

Summary

• GitHub Actions workflow for Vivado bitstream synthesis (manual trigger)
• Uses kkrizka/vivado:2019.2 Docker image (Vivado pre-installed)
• Blinky design: 27-bit counter, M21 clock, R23/T23 LEDs, XC7A100T-1FGG676
• Fix merge conflict in scripts/tri

Closes #305

[github-actions]

📓 NotebookLM Notebook linked to this PR

• Notebook ID: b83263109fb055dc
• URL: https://notebooklm.google.com/notebook/b83263109fb055dc

This notebook contains session context, decisions, and artifacts for this work.

[github-actions]

📓 NotebookLM Notebook linked to this PR

• Notebook ID: b83263109fb055dc
• URL: https://notebooklm.google.com/notebook/b83263109fb055dc

This notebook contains session context, decisions, and artifacts for this work.

[github-actions]

📓 NotebookLM Notebook linked to this PR

• Notebook ID: b83263109fb055dc
• URL: https://notebooklm.google.com/notebook/b83263109fb055dc

This notebook contains session context, decisions, and artifacts for this work.