feat(issued-orders-pdf): true per-page footer (Vystavil + Strana X z Y), sections flow inline

The PDF now carries a real repeating footer on EVERY page via Puppeteer's footerTemplate (Chromium has no CSS margin-box support, so this is the only true footer): 'Vystavil: <logged-in user>' on the left, 'Strana X z Y' / 'Page X of Y' centered, localized by the document language. htmlToPdf gained an optional footerTemplate option (empty header suppresses Chromium's default; bottom margin grows to 18mm). The old body footer pinned by flex min-height is gone. The 'Obsah' sections no longer start a new page with a repeated header - they flow inline right after the items/totals block and paginate naturally (break-inside: avoid per section). Applied at all three render sites (PDF route, ?save=1 archive, /file fallback).

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

src/utils/html-to-pdf.ts

@@ -63,7 +63,23 @@ async function getBrowser(): Promise<Browser> {
   }
 }
 
-export async function htmlToPdf(html: string): Promise<Buffer> {
+export interface HtmlToPdfOptions {
+  /**
+   * Chromium footerTemplate HTML rendered in the bottom margin of EVERY page
+   * — the only true repeating footer Puppeteer supports (CSS @page margin
+   * boxes are not implemented in Chromium). Styles must be inline and the
+   * font-size explicit (Chromium defaults it to 0); `.pageNumber` /
+   * `.totalPages` spans are substituted by Chromium. When set, the bottom
+   * margin grows to make room and an empty headerTemplate suppresses
+   * Chromium's default date/title header.
+   */
+  footerTemplate?: string;
+}
+
+export async function htmlToPdf(
+  html: string,
+  options: HtmlToPdfOptions = {},
+): Promise<Buffer> {
   const b = await getBrowser();
   const page = await b.newPage();
   // Per-request timeouts so one stuck render (e.g. image tag pointing at a
@@ -78,7 +94,19 @@ export async function htmlToPdf(html: string): Promise<Buffer> {
     const pdf = await page.pdf({
       format: "A4",
       printBackground: true,
-      margin: { top: "10mm", bottom: "10mm", left: "10mm", right: "10mm" },
+      margin: {
+        top: "10mm",
+        bottom: options.footerTemplate ? "18mm" : "10mm",
+        left: "10mm",
+        right: "10mm",
+      },
+      ...(options.footerTemplate
+        ? {
+            displayHeaderFooter: true,
+            headerTemplate: "<span></span>",
+            footerTemplate: options.footerTemplate,
+          }
+        : {}),
       timeout: 15_000,
     });
     return Buffer.from(pdf);