feat: full invoice editing before payment, NAS cleanup on date change

- Invoice edit mode now uses the same form as create mode (all fields editable)
- Bank account pre-selected by matching IBAN/account number
- Invoice number read-only in edit mode
- Paid invoices remain read-only
- NAS: old PDF deleted when invoice date changes to different month
- Buttons: Zobrazit fakturu, Uložit, Smazat + status transitions

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/routes/admin/invoices-pdf.ts

@@ -1008,6 +1008,7 @@ ${indentCSS}
           ? new Date(invoice.issue_date)
           : new Date();
         const saveMode = query.save === "1";
+        nasFinancialsManager.cleanIssuedInvoice(invoice.invoice_number!);
         const pdfPromise = htmlToPdf(html)
           .then((pdfBuffer) => {
             nasFinancialsManager.saveIssuedInvoicePdf(

src/services/nas-financials-manager.ts

@@ -30,6 +30,28 @@ class NasFinancialsManager {
 
   // ── Created (issued) invoices ────────────────────────────────────
 
+  /** Remove any existing PDF for this invoice number across all year/month folders */
+  cleanIssuedInvoice(invoiceNumber: string): void {
+    if (!this.basePath) return;
+    const safeName = this.sanitizeFilename(invoiceNumber) + ".pdf";
+    const issuedDir = path.join(this.basePath, DIR_ISSUED);
+    try {
+      if (!fs.existsSync(issuedDir)) return;
+      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 filePath = path.join(yearPath, monthDir, safeName);
+          if (fs.existsSync(filePath)) {
+            fs.unlinkSync(filePath);
+          }
+        }
+      }
+    } catch {
+      // best effort
+    }
+  }
+
   saveIssuedInvoicePdf(
     invoiceNumber: string,
     year: number,