docs: add OpenAPI 3.0 spec for miner HTTP endpoints

[wanruicheng-szyg]

Closes #23

OpenAPI 3.0 specification documenting all miner HTTP endpoints:

• POST /IngestSynapse — store embedding, return CID
• POST /QuerySynapse — ANN search, return top-K results
• POST /ChallengeSynapse — storage proof challenge
• GET /health — liveness probe

Includes sr25519 hotkey signature auth scheme documentation.

Auto-generated from route definitions in neurons/miner.py.

[vercel]

@wanruicheng-szyg is attempting to deploy a commit to the praise's projects Team on Vercel.

A member of the Team first needs to authorize it.