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/deribit/client.py

@@ -11,10 +11,11 @@ from fastapi import HTTPException
 from cerbero_mcp.common import indicators as ind
 from cerbero_mcp.common import microstructure as micro
 from cerbero_mcp.common import options as opt
+from cerbero_mcp.common.candles import validate_candles
 from cerbero_mcp.common.http import async_client
 
 
-def _parse_deribit_response(resp) -> dict:
+def _parse_deribit_response(resp: Any) -> dict[str, Any]:
     """Map Deribit upstream errors to a clean HTTP 502 (retryable) instead of
     leaking JSONDecodeError when the body is HTML (e.g. Cloudflare 5xx page)."""
     if resp.status_code >= 500:
@@ -23,7 +24,8 @@ def _parse_deribit_response(resp) -> dict:
             detail=f"Deribit upstream HTTP {resp.status_code}",
         )
     try:
-        return resp.json()
+        data: dict[str, Any] = resp.json()
+        return data
     except json.JSONDecodeError as e:
         raise HTTPException(
             status_code=502,
@@ -121,10 +123,10 @@ class DeribitClient:
                     resp = await http.get(url, params=request_params, headers=headers)
                     data = _parse_deribit_response(resp)
                     if "result" in data:
-                        return data  # type: ignore[no-any-return]
+                        return data
                 return {"result": None, "error": error_msg}
 
-        return data  # type: ignore[no-any-return]
+        return data
 
     # ── Read tools ───────────────────────────────────────────────
 
@@ -418,24 +420,24 @@ class DeribitClient:
             },
         )
         r = raw.get("result") or {}
-        candles = []
         ticks = r.get("ticks", []) or []
         opens = r.get("open", []) or []
         highs = r.get("high", []) or []
         lows = r.get("low", []) or []
         closes = r.get("close", []) or []
         volumes = r.get("volume", []) or []
-        for idx, ts in enumerate(ticks):
-            if idx >= min(len(opens), len(highs), len(lows), len(closes), len(volumes)):
-                break
-            candles.append({
-                "timestamp": ts,
-                "open": opens[idx],
-                "high": highs[idx],
-                "low": lows[idx],
-                "close": closes[idx],
-                "volume": volumes[idx],
-            })
+        n = min(len(ticks), len(opens), len(highs), len(lows), len(closes), len(volumes))
+        candles = validate_candles([
+            {
+                "timestamp": ticks[i],
+                "open": opens[i],
+                "high": highs[i],
+                "low": lows[i],
+                "close": closes[i],
+                "volume": volumes[i],
+            }
+            for i in range(n)
+        ])
         return {"candles": candles}
 
     async def get_dvol(