Query events from connected calendar accounts

Query events from one account selected by required accountId and a non-empty calendarIds list obtained from the calendar list endpoint. Hidden, unsupported, or foreign calendars are rejected. When no time range is supplied, the range is now through the following three months. A query range may not exceed three months. Recurring events depend on whether the calendar provider returns expanded occurrences; a recurring series that starts outside the range may be omitted even if it has occurrences inside the range. status is complete, partial, or failed. accountErrors gives stable failure codes per account; errorAccountIds remains for compatibility. HTTP 200 with failed means the selected account could not be queried. An unknown or inaccessible account returns 404.