feat(reports): behandlingshistorik as PDF + systemdokumentation pointer and version (#1790)

PR 2 of the behandlingshistorik plan (stacked on #1787).

- lib/reports/behandlingshistorik-pdf-template.tsx: landscape A4 react-pdf
  document. Fixed header (räkenskapsår, urval, legal reference, company) and
  footer (page x of y, generated in Europe/Stockholm), repeated table header,
  wrap={false} rows, no `break` props. Two sections in the order the reader
  needs them: "Ändringar i bokföringssystemet" (p. 9.16 second paragraph)
  then "Bokföringsposter i registreringsordning" (first paragraph). Meta row:
  generated, programversion, antal händelser, källor. Details as one wrapped
  paragraph per row (real-data render 371 events: 1.5 s, 23 pages). Glyphs the
  bundled Helvetica lacks (arrow, true minus) are mapped to ASCII.
- GET /api/reports/behandlingshistorik?format=pdf with a 4 000-event guard
  (413 REPORT_PDF_TOO_LARGE, CSV/XLSX remain complete); PDF first in the
  export menu; catalog exports pdf+xlsx.
- lib/reports/app-version.ts shared by the route and the archive:
  revision/systemdokumentation.json now carries system.version and a
  behandlingshistorik block (where and how it is produced, p. 9.15); the
  shipped systemdokumentation template §9.3 points at Rapporter >
  Behandlingshistorik (PDF/CSV/Excel) as well as the backup ZIP.
- Settings values that are objects render as "key: value" pairs in every
  format; report carries category_filter so the document states its urval.
- Tests: 4 PDF template tests (valid PDF, empty report, filtered range,
  220-row pagination), route pdf 200 + 413, route "unknown format" moved off
  pdf. Prod read-only render verified visually (header, sections, paging).


Claude-Session: https://claude.ai/code/session_01Kw2CFCEt8MxzbJiXMAgMVi

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

lib/errors/structured-errors.ts

@@ -1544,6 +1544,11 @@ const REPORT: Record<string, StructuredErrorEntry> = {
     message_sv: 'Rapporten kunde inte genereras.',
     message_en: 'Failed to generate the report.',
   },
+  REPORT_PDF_TOO_LARGE: {
+    httpStatus: 413,
+    message_sv: 'Rapporten är för stor för PDF. Ladda ner den som CSV eller Excel i stället.',
+    message_en: 'The report is too large for PDF. Download it as CSV or Excel instead.',
+  },
 }
 
 const VAT_REPORT: Record<string, StructuredErrorEntry> = {