Email builder rebuilt: forgiving drag-and-drop, blocks inside columns, and mobile that actually fits

The email builder no longer asks you to aim. Drag-and-drop was rebuilt on a proper drag engine, so blocks land where you're pointing instead of needing a precise hit on a thin line - and you can now drag blocks straight into a column, between columns, and back out again, rather than adding them through a settings panel. Dragging is forgiving in both directions: drop into empty column space to append, or onto an existing block to place it exactly there. 2, 3 and 4 columns are now three separate blocks in the palette instead of one block you had to reconfigure after dropping. Mobile rendering is fixed properly: multi-column rows now stack full-width on phones and images shrink to fit the screen instead of casting off the side, so the Mobile preview shows what recipients actually get. A block set to zero top padding now renders with zero top padding - the stray white gap above the first block is gone. Images changed too: the free-text image URL box is gone (it only ever let broken, unhosted links into emails), uploads now go straight into your Content Library so anything you add in an email is available everywhere else, and you can pick from the library - folders and all - without leaving the builder. Replacing an image no longer stacks up a growing pile of thumbnails; you see the current image with Replace, Library and Remove. Finally, the builder now saves reliably: an edit made in the moment before you click away is written rather than dropped, which is what made work occasionally vanish on return. The same fix covers the campaign Recipients step.