Add EUR/USD support with modular per-pair signal producer pattern

- Register EUR/USD in config (pip 0.0001, EurUsdStrategyConfig)
- Create pair_signals/ module: registry + dispatcher with per-pair
  config factories (xauusd.py, eurusd.py) for easy add/remove
- EUR/USD gets forex-tuned regime weights, London+NY session hours,
  XAU strategy gates disabled
- Add defense-in-depth display_name guards in signal_aggregator
- Rename telegram_bot.py → testing_telegram_bot.py with separate
  bot token, both pairs with dedicated button rows
- Add EUR/USD to news engine affected pairs map
- 9 new tests (146 total, all passing)
- Zero changes to engine.py, data_provider.py, main.py, backtest/

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pair_signals/xauusd.py

@@ -0,0 +1,23 @@
+"""XAU/USD signal producer config."""
+
+from typing import Optional, List
+from config import PlatformConfig, Timeframe
+
+_CONFIRMATIONS = {
+    Timeframe.M5:  [Timeframe.M15, Timeframe.H1],
+    Timeframe.M15: [Timeframe.M5, Timeframe.H1],
+    Timeframe.H1:  [Timeframe.M15, Timeframe.H4],
+    Timeframe.H4:  [Timeframe.H1, Timeframe.D1],
+}
+
+
+def make_config(
+    primary_tf: Timeframe,
+    confirmation_tfs: Optional[List[Timeframe]] = None,
+) -> PlatformConfig:
+    config = PlatformConfig()
+    config.primary_timeframe = primary_tf
+    config.confirmation_timeframes = (
+        confirmation_tfs or _CONFIRMATIONS.get(primary_tf, [Timeframe.M15, Timeframe.H4])
+    )
+    return config