feat(consensus): server-side PoW dual-mining proof verification engine (#453) - #8448

Server-Side PoW Dual-Mining Proof Verification Engine

Closes: Scottcjn/rustchain-bounties#453
Bounty Reward: 75 RTC (~$7.50 USD)

Summary & Deliverables

This PR implements the master server-side verification subsystem for PoW dual-mining (Ergo, Monero, Warthog, Kaspa, Verus, Alephium, Zephyr, Neoxa):

1. Table Schema (node/pow_dual_mining_verification.py:init_pow_tables):

   • Creates pow_mining_proofs with composite primary key (miner, epoch, chain).
   • Adds pow_bonus column to miner_attest_recent.

2. Proof Validation Pipeline (validate_pow_proof):

   • Tier 1.50x Node RPC Proof: Verifies active mining candidate, peer sync, and chain-specific plausible height floors (e.g. Ergo >= 1,000,000, Monero >= 3,000,000).
   • Tier 1.30x Pool Account Proof: Validates verified hashrate > 0 and pool URL whitelist.
   • Tier 1.15x Process Detection: Validates process name heuristics against allowed miners (xmrig, wart-miner, ergo-miner, ccminer, etc.) with PID checks.
   • Anti-Cheat & Hardening: Strict nonce binding (rejection of <8 char nonces), replay protection (single proof per miner per epoch per chain), and proof expiration window (max age 900s).

3. Automated Test Suite (node/tests/test_pow_dual_mining_verification.py):

   • 10/10 tests PASS covering all proof tiers, edge cases, height boundaries, and replay resistance.

Payout Details

• Native RTC: RTC8b1fb717791b0a7b72649342b5c7c7bd822786af
• Base USDC: 0x85A19c533C87CcbF9459b609C05c733BF189890e
• Solana USDC: HynBYxN6Sh5p4iJqUAz1Xboswb9KBKzzjCqDUwEPY2Be