Data layer for `` (widget files never inline fetch — `useContactSubmission` split). Availability: plain `useState`/`useEffect`/`AbortController` self-fetch through `contentFetch`, unconditional post-mount refetch even when SSR-seeded. Booking: single POST with a `submitting` lock; errors map to typed `MeetingBookingErrorCode`s (unknown → `TEMPORARILY_UNAVAILABLE`). `setMonthOffset` clamps to `MAX_MONTH_OFFSET`.