feat: add 0x402 trading signals service

AI-optimized compound trading signals via MPP on Tempo mainnet.
Cross-references SEC Form 4 insider trades, congressional stock activity,
and market data through an AutoResearch-tuned scoring engine.

6 endpoints:
- GET /api/signals/scan ($0.02) — Top compound signals
- GET /api/signals/score ($0.01) — Score specific ticker
- GET /api/insider/cluster-buys ($0.005) — Insider cluster buys
- GET /api/insider/officer-sells ($0.005) — Officer sells
- GET /api/congress/recent ($0.005) — Congressional trades
- GET /api/market/dashboard ($0.005) — Market overview

Live: https://0x402.link
Docs: https://0x402.link/llms.txt

Author: hermes-agent