lint: ruff clean services/ (autofix + manual + ignore E741)

- 24 autofix safe (SIM105 contextlib.suppress, F401 unused imports,
  I001 import order, B007 unused loop var, F811 redef, F841 unused).
- 15 unsafe-fix (UP038 X|Y in isinstance, SIM108 ternary, ecc.).
- Manual fix: SIM102 nested if in deribit term_structure, E402 imports
  in test_cot.py + sentiment server.py.
- Ignore E741 (variabili 'l' in list comprehensions deribit/client.py
  — stilistico, non bug).

Tests: 478/478 verdi.

services/mcp-deribit/src/mcp_deribit/client.py

@@ -1,10 +1,10 @@
 from __future__ import annotations
 
+import contextlib
 import time
 from dataclasses import dataclass, field
 from typing import Any
 
-import httpx
 from mcp_common import indicators as ind
 from mcp_common import microstructure as micro
 from mcp_common import options as opt
@@ -196,10 +196,8 @@ class DeribitClient:
             name = s.get("instrument_name")
             oi = s.get("open_interest")
             if name and oi is not None:
-                try:
+                with contextlib.suppress(TypeError, ValueError):
                     oi_by_name[name] = float(oi)
-                except (TypeError, ValueError):
-                    pass
 
         all_items = raw.get("result") or []
         filtered: list[dict] = []
@@ -882,10 +880,9 @@ class DeribitClient:
                 shape = "backwardation"
             short_term = next((x for x in ts if 8 <= x["dte"] <= 14), None)
             mid_term = next((x for x in ts if 35 <= x["dte"] <= 45), None)
-            if short_term and mid_term:
-                if mid_term["atm_iv"] - short_term["atm_iv"] > 5:
-                    contango_steep = True
-                    calendar_opp = True
+            if short_term and mid_term and mid_term["atm_iv"] - short_term["atm_iv"] > 5:
+                contango_steep = True
+                calendar_opp = True
 
         return {
             "currency": currency,
@@ -1131,7 +1128,7 @@ class DeribitClient:
 
         structure = self._guess_structure(enriched)
 
-        notional = sum(l["quantity"] * spot for l in enriched) if spot else 0.0
+        sum(l["quantity"] * spot for l in enriched) if spot else 0.0
         fee_per_leg = min(0.0003 * (spot or 1) * sum(l["quantity"] for l in enriched),
                            0.125 * abs(net_premium)) if spot else 0.0
         fees_open = round(fee_per_leg, 4)

services/mcp-deribit/src/mcp_deribit/server.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import contextlib
 import os
 
 from fastapi import Depends, FastAPI, HTTPException
@@ -272,10 +273,8 @@ def create_app(
     @asynccontextmanager
     async def _lifespan(_app: FastAPI):
         for inst in ("BTC-PERPETUAL", "ETH-PERPETUAL"):
-            try:
+            with contextlib.suppress(Exception):
                 await client.set_leverage(inst, cap_default)
-            except Exception:
-                pass
         yield
 
     app = build_app(
@@ -551,10 +550,8 @@ def create_app(
         _check(principal, core=True)
         lev = _enforce_leverage(body.leverage, creds=creds, exchange="deribit")
         if lev != cap_default:
-            try:
+            with contextlib.suppress(Exception):
                 await client.set_leverage(body.instrument_name, lev)
-            except Exception:
-                pass
         result = await client.place_order(
             instrument_name=body.instrument_name,
             side=body.side,
@@ -582,10 +579,8 @@ def create_app(
         lev = _enforce_leverage(body.leverage, creds=creds, exchange="deribit")
         if lev != cap_default:
             for leg in body.legs:
-                try:
+                with contextlib.suppress(Exception):
                     await client.set_leverage(leg.instrument_name, lev)
-                except Exception:
-                    pass
         result = await client.place_combo_order(
             legs=[leg.model_dump() for leg in body.legs],
             side=body.side,