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>

config.example.json

@@ -0,0 +1,22 @@
+{
+  "mode": "paper",
+  "poll_seconds": 12,
+  "watchlist": [],
+  "bankroll_usd": 1000.0,
+  "bankroll_pct": 0.02,
+  "price_guard_pct": 0.05,
+  "risk": {
+    "max_trade_usd": 50.0,
+    "daily_spend_cap_usd": 250.0,
+    "max_total_exposure_usd": 500.0,
+    "max_open_positions": 20,
+    "min_price": 0.05,
+    "max_price": 0.95,
+    "min_order_usd": 5.0
+  },
+  "live": {
+    "private_key": "",
+    "funder_address": "",
+    "signature_type": 1
+  }
+}