Add Netlify background upload scaffolding

[snissn]

Closes #76

Summary

This is the first implementation slice for Netlify-hosted Filecoin Onchain Cloud uploads without a VPS.

Included here

• THS support for app.deploy.netlify.uploads
• linting that requires app.features.uploads=true when Netlify uploads are configured
• th build emission of:
  • netlify.toml
  • Netlify function scaffolding for upload start/status/background worker
  • a small generated deployment README
• manifest upload endpoint wiring for the generated Netlify paths
• microblog example opt-in to the Netlify upload deployment target
• tests for THS validation/lint and build artifact emission

Next

• validate/improve the generated Netlify function runtime behavior against a real Netlify deployment
• tighten docs and deployment ergonomics
• wire any remaining provider/runtime edge cases

[snissn]

Live Netlify validation completed against the generated microblog deploy.

Validated site:

• https://tokenhost-microblog-1774417572.netlify.app

What was verified:

• GET /__tokenhost/upload returns enabled filecoin_onchain_cloud / netlify-background status
• POST /__tokenhost/upload returns 202 with a jobId
• polling /__tokenhost/upload-status?jobId=... settles to ok: true
• final payload includes a real gateway URL + CID from FOC

Concrete success payload from the live job:

• url: https://caliberation-pdp.infrafolio.com/piece/bafkzcibev7macddl4bkyuusf4s4sjhecf25pci65736ydw7bctgpgodau7oxqtm2g4
• cid: bafkzcibev7macddl4bkyuusf4s4sjhecf25pci65736ydw7bctgpgodau7oxqtm2g4

Final fix in this push:

• generated Netlify worker now writes the foc-cli config file directly in the function temp HOME instead of relying on broken wallet init behavior in a fresh serverless runtime.