feat(V2): shared Candle validator + uniform 'candles' response key

Introduce common/candles.py with a Pydantic Candle model enforcing OHLC
consistency (high≥max, low≤min), non-negative volume and positive
timestamp. validate_candles() coerces upstream rows, sorts by timestamp
and raises HTTPException(502) on malformed data — surfacing upstream
data corruption as a retryable envelope instead of silently returning
nonsense.

Wired into all five exchange historical endpoints (Bybit, Hyperliquid,
Deribit, Alpaca, IBKR). BREAKING: Alpaca get_bars and IBKR get_bars now
return 'candles' (was 'bars') to align with the other exchanges.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/cerbero_mcp/exchanges/bybit/client.py

@@ -22,6 +22,7 @@ import httpx
 
 from cerbero_mcp.common import indicators as ind
 from cerbero_mcp.common import microstructure as micro
+from cerbero_mcp.common.candles import validate_candles
 
 BASE_MAINNET = "https://api.bybit.com"
 BASE_TESTNET = "https://api-testnet.bybit.com"
@@ -254,18 +255,17 @@ class BybitClient:
             params["end"] = end
         resp = await self._request_public("GET", "/v5/market/kline", params=params)
         rows = (resp.get("result") or {}).get("list") or []
-        rows_sorted = sorted(rows, key=lambda r: int(r[0]))
-        candles = [
+        candles = validate_candles([
             {
                 "timestamp": int(r[0]),
-                "open": float(r[1]),
-                "high": float(r[2]),
-                "low": float(r[3]),
-                "close": float(r[4]),
-                "volume": float(r[5]),
+                "open": r[1],
+                "high": r[2],
+                "low": r[3],
+                "close": r[4],
+                "volume": r[5],
             }
-            for r in rows_sorted
-        ]
+            for r in rows
+        ])
         return {"symbol": symbol, "candles": candles}
 
     async def get_indicators(