Lists dashboards using bidirectional cursor pagination: Whippy's built-in dashboards first,
in a fixed order, followed by the organization's saved dashboards (newest first).

A dashboard is a collection of metrics. The individual charts are exposed
separately under /v1/metrics.

Built-in dashboards (source: whippy) are the standard Agents, Conversations, Campaigns,
Calls, and Usage analytics. They have stable reserved IDs (prefix 00000000-0000-4000-) and
null created_at/updated_at. Saved dashboards (source: organization) are sorted by
created_at descending, with id as a tiebreaker.

Pagination

• First page: omit cursor (or use direction=forward, the default).
• Next page: use metadata.next_cursor with direction=forward.
• Previous page: use metadata.prev_cursor with direction=backward.
• direction=backward without cursor: returns 422.
• offset: not supported.

Cursors are opaque, base64-encoded tokens that decode to {"inserted_at": "<ISO8601>", "id": "<uuid>"}.

Filtering

• source — optionally filter by whippy (built-in dashboards) or organization
  (dashboards saved in the organization). Omitting it returns both.