Explore gets a Dashboards tab for laying out shared widgets

Explore's Widgets tab now has a companion Dashboards tab: lay saved widgets out on a shared 12-column grid that everyone in the project sees the same way. Any member can create a dashboard and add the project's saved widgets to it (the same widget can be placed more than once, and editing it updates every placement); its creator or anyone with project write access can drag and resize cards. A dashboard can be renamed, duplicated with its own independent copies of its widgets, and deleted. Widgets also gained a Cards view, the dashboard's own date presets, and a shared filter bar that every widget on a page answers within.

Features

Lay saved widgets out on a dashboard — Create a dashboard from the project's saved widgets, drag and resize its cards on a 12-column grid, and share it with everyone in the project. Duplicating a dashboard copies its widgets too, so the copy is fully independent, and every change autosaves as it lands. (#7175, @subomi; #7173, @subomi)
A shared filter bar and time range for everything on a page — Widgets and Explore now share the dashboard's date presets (15 minutes to 90 days), and a page's date range and filters apply to every widget placed on it: the page's range replaces each widget's own window, page filters are ANDed with each widget's own filters, and dragging across a time chart narrows the page. (#7122, @subomi; #7121, @subomi)
A Cards view for the Widgets tab — Toggle between List and Cards to see every saved widget drawn as a card, answering its own question, with the same actions as its row. Each card runs its query only once it scrolls into view. (#7133, @subomi)
See where a widget is used before you change it — The Widgets tab gets a Dashboards column counting the dashboards a widget is on and naming them on hover; saving edits to a widget on a dashboard, or deleting it, now says which dashboards that reaches. (#7177, @subomi; #7174, @subomi)