Add OCR language override setting

Operators can now choose Tesseract language pack(s) per profile via a
sidebar select (#optOcrLang) and profile editor (#peOptOcrLang). Presets:
dan+eng (default), dan, eng, dan+eng+deu, dan+eng+swe, dan+eng+fra. The
ocr_lang option flows from the UI through all three scan engines (M365
files/attachments, Google Drive, Gmail) down to document_scanner.scan_pdf
and scan_image — including the spawned PDF-OCR subprocess worker.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

static/js/scan.js

@@ -127,6 +127,7 @@ function buildScanPayload() {
     scan_photos:      document.getElementById('optScanPhotos') ? document.getElementById('optScanPhotos').checked : false,
     skip_gps_images:  document.getElementById('optSkipGps') ? document.getElementById('optSkipGps').checked : false,
     min_cpr_count:    document.getElementById('optMinCpr') ? (parseInt(document.getElementById('optMinCpr').value) || 1) : 1,
+    ocr_lang:         document.getElementById('optOcrLang')?.value || 'dan+eng',
     scan_emails:      document.getElementById('optScanEmails') ? document.getElementById('optScanEmails').checked : false,
     scan_phones:      document.getElementById('optScanPhones') ? document.getElementById('optScanPhones').checked : false,
     retention_enabled: document.getElementById('optRetention') ? document.getElementById('optRetention').checked : false,