feat(bench200): on-chain Solana fee parser, Phantom, dust filter

[Flotapponnier]

Summary

• Replace Mobula fee fields (all zero) with direct Solana RPC tx parsing via getTransaction
• Three-layer fee detection: gas + known platform wallet owners + small SOL/USDC heuristic recipients
• Fomo fee wallet confirmed on-chain (R4rNJHaffSUotNmqSKNEfDcJE8A7zJUkaoM5Jkd7cYX)
• Filter dust trades < $5 that make gas dominate at tiny sizes
• Add Phantom as a provider
• Remove platformFeeUSD / platformGasUSD metrics (no longer computed separately)
• AMM LP fees explicitly excluded from scope (same for all frontends)

Test plan

• Build passes (go build ./...)
• Deploy on VPS: docker build --no-cache + docker stop/rm/run
• First poll: Fomo should show ~1%, pump-fun ~0.02% (gas only)
• Check Prometheus memecoin_platform_fee_pct and memecoin_platform_trade_count