feat(documents)!: unify offers and issued orders end to end

One coherent pass over the two sibling document models, driven by a 3-lens
1:1 scan (~60 divergences inventoried) + user decisions. Migration adds
issued_orders.locked_by/locked_at and the issued_order_sections table
(mirror of scope_sections; applied to dev + test DBs).

Issued orders gained (offers as reference implementation):
- rich-text SECTIONS with CZ/EN titles, rendered on their own PDF page in
  the PO template's red style (shared DocumentSectionSchema, one-transaction
  create/update incl. items - fixes a torn-write bug)
- edit LOCKING (lock/heartbeat/unlock routes, 423 + holder name, 30s TTL =
  3 missed 10s heartbeats; locked_by enrichment on detail)
- archived-PDF serving: GET /:id/file reads the NAS copy (new
  readIssuedByNumber sweep) with live-render fallback + re-archive; offers'
  /file got the same fallback (kills the 'ulozte nabidku' dead end)
- NAS cleanup on delete, in-tx po_number uniqueness (409), collision-advancing
  number previews (also invoice previews), PUT returns assigned po_number

Offers hardened (issued as reference):
- VALID_TRANSITIONS enforced (no more numberless 'ordered' offers; invalidate
  follows the table; order creation only from active offers) +
  valid_transitions on detail
- explicit 400 instead of silent edits outside draft/active (mirrored on
  issued: explicit 400 replaced silent drops)
- customer existence check + Number(null)->0 clear bug fixed; delete of a
  linked offer -> 409 instead of P2003 500; error-token convention; Zod caps
  DB-aligned (desc 500/unit 20/number 50/project_code 100, isoDateString
  dates, ints for positions); audit old/new values + koncept fallbacks;
  list id tiebreaks; stats include trimmed; NAS delete dedupe

Frontend unification (6 new shared modules):
- components/document/{DocumentItemsEditor,SectionsEditor,LockBanner}
- hooks/{useDocumentLock,useUnsavedChangesGuard,useDocumentPdf(+list variant)}
- OfferDetail 1940->1100 lines, IssuedOrderDetail 1400->980: headline-only
  document number (form field removed), one form layout/readonly convention,
  view-permission opens read-only everywhere (issued's editable-for-viewers
  hole closed), server-driven transition buttons, dirty guard + Enter submit
  on both, useApiMutation everywhere (new opt-in envelope mode), fixed
  infinite spinner on failed detail fetch, draft PDFs hidden (no number yet)
- lists: supplier filter + count line on issued, Mena column dropped + mono
  numbers on offers, shared hardened per-row PDF flow (spinner, double-click
  guard, 401 close, blob cleanup), proper Czech quotes, real CTA empty
  states, query-lib cleanups (["offers","customers"] key, typed list rows,
  shared CurrencyAmount, retry:false on details)
- pdf-shared.ts: one escapeHtml/cleanQuillHtml(strict)/formatNum(NBSP)/
  formatCurrency/formatDate for all four PDF routes; offer PDF keeps its
  monochrome look (fractional qty fix: 1.5 no longer prints as 2); issued
  PDF language now comes from the document column

+49 tests (suite 364 -> 413). Each stage passed an independent review; final
cross-stage integration review verified the FE<->BE contracts.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/services/nas-financials-manager.ts

@@ -119,6 +119,54 @@ export class NasDocumentManager {
     }
   }
 
+  /**
+   * Locate and read the archived PDF for an issued document by its number
+   * alone, sweeping every Vydané/YYYY/MM folder (the same walk cleanIssued
+   * uses). Needed because the archive folder is derived from the document
+   * date at save time and the date can be edited afterwards — a fixed
+   * expected-path read would miss a file that does exist in another month
+   * folder. Returns null when not found (callers fall back to a live render).
+   */
+  readIssuedByNumber(
+    documentNumber: string,
+  ): { data: Buffer; fileName: string } | null {
+    if (!this.basePath) return null;
+    const safeName = this.sanitizeFilename(documentNumber) + ".pdf";
+    const issuedDir = path.join(this.basePath, DIR_ISSUED);
+    try {
+      if (!fs.existsSync(issuedDir)) return null;
+      for (const yearDir of fs.readdirSync(issuedDir)) {
+        const yearPath = path.join(issuedDir, yearDir);
+        if (!fs.statSync(yearPath).isDirectory()) continue;
+        for (const monthDir of fs.readdirSync(yearPath)) {
+          const monthPath = path.join(yearPath, monthDir);
+          try {
+            if (!fs.statSync(monthPath).isDirectory()) continue;
+          } catch (err) {
+            console.error(
+              "[nas-financials-manager] stat failed for monthPath:",
+              monthPath,
+              err,
+            );
+            continue;
+          }
+          const filePath = path.join(monthPath, safeName);
+          if (fs.existsSync(filePath)) {
+            return { data: fs.readFileSync(filePath), fileName: safeName };
+          }
+        }
+      }
+      return null;
+    } catch (err) {
+      console.error(
+        "[nas-financials-manager] readIssuedByNumber failed for:",
+        documentNumber,
+        err,
+      );
+      return null;
+    }
+  }
+
   readIssued(relativePath: string): { data: Buffer; fileName: string } | null {
     const fullPath = this.resolveSafePath(relativePath);
     if (!fullPath) return null;