deploy: TP01 trend portfolio (PORT LF4h) module + paper trader

- src/strategies/trend_portfolio.py: canonical winner, causal/no-leakage,
  reproduces CAGR +16.5% Sharpe 1.36 maxDD 13.8%
- scripts/live/paper_trend.py: forward-only paper trader, persistent state, resume
- tests/test_trend_portfolio.py: 5 tests (causality, profitability, long-only, paper parity)

data/paper_trend/state.json

@@ -0,0 +1,13 @@
+{
+  "capital": 2000.0,
+  "initial_capital": 2000.0,
+  "start_ts": 1781884800000,
+  "last_ts": 1781884800000,
+  "positions": {
+    "BTC": 0.0,
+    "ETH": 0.0
+  },
+  "n_bars": 0,
+  "peak": 2000.0,
+  "max_dd": 0.0
+}