feat(desktop): show a server nest's MaterialLedger holds and closeout note

Server nests in Database mode get a read-only status bar label comparing their
open MaterialLedger holds with the sheets they cut, e.g. "Ledger: 2 of 4 held,
2 short". Nothing writes to the ledger and nothing waits on it.

- MaterialLedgerClient.GetHoldsAsync reads GET /api/stock/holds?openNestNestId=
  with the closed LedgerHoldsResult set; unknown status strings are kept. The
  request plumbing is shared with GetStockAsync.
- LedgerHoldSummary (OpenNest.Data) counts Proposed/Approved/Released/
  AwaitingCloseout holds against the plate quantities, skipping the trailing
  empty plate as /sheets does.
- NestHoldStatus refreshes on server open, after save, after storage or
  Options changes and on label click; it never polls. The tooltip lists holds
  in nest units. File-mode, unsaved and ledger-less nests show nothing.
- Setting Has Been Cut in Nest Info with holds still open shows a non-modal
  note linking to {ledgerUrl}/Nests/{id}. Posting is not gated.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/automatic-nesting.md

@@ -330,3 +330,6 @@ with its own benchmark.
 
 MCP, Console and `OpenNest.Api` do not load ledger stock yet. The client and mapper live
 in `OpenNest.Data`, so these front ends can use them.
+
+The status bar shows a server nest's ledger holds and reminds you to close them out once
+the nest is cut; see [MaterialLedger holds](nest-storage.md#materialledger-holds-desktop).