Add 4-pair candle-boundary auto-scanner (free tier safe)

Expand from 2 to 4 pairs (EUR/USD, USD/JPY, GBP/USD, XAU/USD) with
automatic scanning at M15 and H1 candle close boundaries. Scheduler
staggers H1 by 60s to stay within 8 credits/min; daily budget is
480 of 800 allowed. Cache TTL is now candle-duration-aware so cross-TF
confirmation data is reused without extra API calls. Spread estimate
uses primary-TF data instead of fetching M5 separately.

config.py

@@ -38,10 +38,14 @@ class MarketSession(Enum):
 # ── Supported pairs ──────────────────────────────────────────────
 USDJPY = "USDJPY=X"
 EURUSD = "EURUSD=X"
+GBPUSD = "GBPUSD=X"
+XAUUSD = "XAUUSD=X"
 
 PAIR_INFO = {
     USDJPY: {"display": "USD/JPY", "pip_value": 0.01, "is_jpy_pair": True},
     EURUSD: {"display": "EUR/USD", "pip_value": 0.0001, "is_jpy_pair": False},
+    GBPUSD: {"display": "GBP/USD", "pip_value": 0.0001, "is_jpy_pair": False},
+    XAUUSD: {"display": "XAU/USD", "pip_value": 0.10, "is_jpy_pair": False},
 }
 
 # Defaults (kept for backward compat)
@@ -117,7 +121,7 @@ class SignalConfig:
 @dataclass
 class NewsConfig:
     """Economic calendar & sentiment."""
-    tracked_currencies: List[str] = field(default_factory=lambda: ["USD", "JPY", "EUR"])
+    tracked_currencies: List[str] = field(default_factory=lambda: ["USD", "JPY", "EUR", "GBP"])
     min_impact: str = "medium"
     pre_event_buffer_minutes: int = 30
     post_event_buffer_minutes: int = 15
@@ -163,4 +167,12 @@ class PlatformConfig:
 
     refresh_interval: int = 300
 
+    scan_pairs: List[str] = field(
+        default_factory=lambda: [EURUSD, USDJPY, GBPUSD, XAUUSD]
+    )
+    scan_timeframes: List[Timeframe] = field(
+        default_factory=lambda: [Timeframe.M15, Timeframe.H1]
+    )
+    candle_buffer_seconds: int = 10
+
     log_level: str = "INFO"