Add copy-trade engine: mirror watched wallets' entries and exits

Watches a wallet list and copies trades onto your account: % -of-bankroll
sizing, proportional entry/exit mirroring, 5% price guard, and a no-backfill
rule for positions held before start. Paper mode by default; live trading is
gated behind config + --live + a typed confirmation, with hard risk caps
(per-trade, daily, total exposure, open positions, price bounds). Live
execution via py-clob-client (lazy import). Credentials/state gitignored.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.gitignore

@@ -1,3 +1,8 @@
 __pycache__/
 *.pyc
 .DS_Store
+
+# never commit live credentials or runtime state
+config.json
+copytrade_state.json
+*.tmp