merge: integrate refactor/menubar-reorg

Brings in the Plate menu reorganization, Database-mode drag-and-drop
open, the SavedNestsForm look fixes and the Irregular block-fill work
budget fix.

Conflicts:
- MainForm.Designer.cs: keep the branch's Plate menu order (Arrange
  submenu, View in CAD last) and add master's Plan Cutting item ahead
  of the lead-in commands.
- SavedNestsForm.cs: keep master's browser rewrite (details, preview,
  columns) and apply the branch's intent to it: open maximized with
  MaximizedBounds clear of the taskbar, the lighter grid palette on all
  three grids, and B/KB/MB/GB file sizes.

docs/nest-storage.md

@@ -26,6 +26,13 @@ The desktop app can save nests two ways:
   file to share or back up. Export does not change the document's file save path
   or database record association.
 
+Dragging one or more `.nest` files onto the main window (or onto an open
+plate) opens them from disk directly, in either mode — this is the only way
+to open a local file while in Database mode, since Open there browses server
+records instead of showing a file dialog. A document opened this way is not
+bound to a server record, so a subsequent Save in Database mode creates a new
+record on first save, same as any other unbound document.
+
 The mode and server address are stored per-PC at `%APPDATA%\OpenNest\storage.json`
 (`OpenNest.Data.NestStorageSettings`), defaulting to File mode so existing
 installs are unaffected until an operator opts in via **File > Storage Mode...**.