feat: Decentralized GPU Render Protocol — RTC Payment Layer (Bounty #30, 100 RTC)

[AliaksandrNazaruk]

Bounty #30 — Decentralized GPU Render Protocol (100 RTC)

Implements the complete GPU Render Protocol as specified in issue #30.

What's included:

GPU Node Attestation:

• Register/update GPU nodes with hardware specs (model, VRAM, CUDA/ROCm version)
• Hardware fingerprinting to prevent spoofing
• Support for nvidia_gpu, amd_gpu, apple_gpu device architectures
• Capability flags: render, TTS, STT, LLM
• Supported model lists (TTS voices, LLM models)

Escrow Payment Endpoints:

• POST /render/escrow — Lock RTC for render jobs
• POST /voice/escrow — Lock RTC for TTS/STT jobs
• POST /llm/escrow — Lock RTC for inference jobs
• POST /render|voice|llm/release — Release to GPU provider on completion
• POST /render/refund — Refund on job failure
• GET /render/escrow/<job_id> — Check escrow status

Pricing Oracle:

• Fair market rate calculation from active GPU node pricing
• Price manipulation detection (flags >3x avg or <0.1x min)
• Historical pricing records
• Separate rate tables for render, TTS, STT, LLM

Database:

• SQLite with WAL mode for concurrent access
• render_escrow table with status tracking
• gpu_attestations table with full spec storage
• pricing_history table for oracle data

Integration:

• Flask route registration via register_routes(app)
• Works with existing RustChain node architecture
• Compatible with BoTTube render marketplace (docs: add API reference, miner setup guide, and Python SDK tutorial (Bounty #72) #39)

Tests

12 unit tests, all passing ✅

Closes #30