fix(api-client): Use ApiClientError for non-JSON 400 responses

[sentry]

Previously, SentryApiService.parseJsonResponse would throw a plain Error when it encountered a non-JSON response (e.g., HTML) for a 400 Bad Request. This plain Error was not recognized by isExpectedToolError as an expected API client error, causing it to be incorrectly logged as an unhandled exception in Sentry.

This change updates parseJsonResponse to use createApiError(...) instead of throw new Error(...) for both the HTML and generic non-JSON fallback paths. This ensures that these 400 responses are correctly classified as ApiClientError (specifically ApiValidationError), which isExpectedToolError will then suppress, preventing unnecessary Sentry alerts.

Fixes MCP-SERVER-G2E

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