chore: ruff cleanup — fix 7 long-standing lint findings

Mechanical, no behavior change. `ruff check src/ tests/` now passes
with zero findings.

- cli.py:147 (SIM105) — replace `try/except SynologyError/pass` around
  the cleanup logout with `contextlib.suppress(SynologyError)`.
- compose.py:271 (B007) — drop the unused `i` from the env_list
  preview-detection loop (the apply loop below still uses enumerate).
- compose.py:329 (E501) — extract `verb = "Updated" if … else "Added"`
  into a local before the return so the f-string fits in 100 cols.
- images.py:237 (E501) — extract `stopped_name = in_use_stopped[0]`
  before the return and split the message across two f-strings.
- test_auth.py:38, 127, 140 (SIM117) — combine nested `with patch(…):`
  / `with pytest.raises(…):` into single parenthesised with-statements.

236 tests pass.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/test_auth.py

@@ -35,9 +35,11 @@ def test_resolve_credentials_no_credentials(monkeypatch):
     config = make_config()
     auth = AuthManager(config)
 
-    with patch("keyring.get_password", return_value=None):
-        with pytest.raises(AuthenticationError, match="No credentials found"):
-            auth.resolve_credentials()
+    with (
+        patch("keyring.get_password", return_value=None),
+        pytest.raises(AuthenticationError, match="No credentials found"),
+    ):
+        auth.resolve_credentials()
 
 
 def test_resolve_credentials_from_keyring(monkeypatch):
@@ -124,9 +126,11 @@ async def test_login_2fa_required():
     mock_client = AsyncMock()
     mock_client.request.side_effect = SynologyError("2FA required", code=403)
 
-    with patch.object(auth, "resolve_credentials", return_value=("user", "pass", None)):
-        with pytest.raises(AuthenticationError, match="2FA is required"):
-            await auth.login(mock_client)
+    with (
+        patch.object(auth, "resolve_credentials", return_value=("user", "pass", None)),
+        pytest.raises(AuthenticationError, match="2FA is required"),
+    ):
+        await auth.login(mock_client)
 
 
 @pytest.mark.asyncio
@@ -137,9 +141,11 @@ async def test_login_no_sid_returned():
     mock_client = AsyncMock()
     mock_client.request.return_value = {}  # No 'sid' key
 
-    with patch.object(auth, "resolve_credentials", return_value=("user", "pass", None)):
-        with pytest.raises(AuthenticationError, match="no session ID"):
-            await auth.login(mock_client)
+    with (
+        patch.object(auth, "resolve_credentials", return_value=("user", "pass", None)),
+        pytest.raises(AuthenticationError, match="no session ID"),
+    ):
+        await auth.login(mock_client)
 
 
 @pytest.mark.asyncio