Add RustChain - Proof-of-Antiquity blockchain

[Scottcjn]

Summary

Adds RustChain to the Blockchains section.

RustChain implements a novel Proof-of-Antiquity consensus mechanism that rewards real vintage hardware (PowerPC G4/G5, Pentium 4, etc.) with higher mining multipliers. It uses 6-point hardware fingerprinting (clock drift, cache timing, SIMD identity, thermal drift, instruction jitter, anti-emulation) to verify authentic hardware and prevent VM spoofing.

Key features:

• Ed25519 elliptic curve digital signatures
• BIP39 24-word mnemonic seed phrases
• Ergo blockchain anchoring for cross-chain verification
• RIP-200 round-robin 1-CPU-1-Vote consensus
• Time-aged antiquity multipliers (e.g., G4 = 2.5x, G5 = 2.0x)

The entry is placed in alphabetical order in the Blockchains section, following the existing format.