feat(ui): shared record-scoped useDocumentDraft hook; fix half-wired invoice draft banner; dedupe draft keys

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/admin/lib/draftKeys.ts

@@ -0,0 +1,12 @@
+/**
+ * Single source of truth for the localStorage keys used by the document-draft
+ * autosave feature. Both the form (write side) and the list/banner (read side)
+ * MUST import the key from here — duplicating the string literal in two files
+ * means changing one silently breaks the other (the banner stops matching).
+ */
+export const DRAFT_KEYS = {
+  offer: "boha_offer_draft",
+  invoice: "boha_invoice_draft",
+} as const;
+
+export type DraftKey = (typeof DRAFT_KEYS)[keyof typeof DRAFT_KEYS];