fix(kml-import): address PR #488 review issues

- Strip BOM (U+FEFF) from 14 translation files injected by editor
- Guard KMZ unpack against zip-bomb: check entry.uncompressedSize against
  50 MB cap (KMZ_DECOMPRESSED_SIZE_LIMIT) before calling .buffer();
  limit is an exported constant so tests can override it
- Fix non-BMP HTML entity decoding: replace String.fromCharCode with
  String.fromCodePoint + 0x10FFFF bounds check so emoji like 😀
  round-trip correctly
- Switch KML namespace stripping from regex to fast-xml-parser's
  removeNSPrefix option; XMLValidator accepts namespaced XML natively,
  making the pre-strip step unnecessary
- Remove dead skippedCount overwrite after transaction; per-loop
  increment already tracks it alongside per-item error messages
- Type multer req.file as Express.Multer.File on both /import/gpx
  and /import/map routes instead of (req as any).file
- Add unit tests: emoji entity decoding (decimal + hex), KMZ zip-bomb
  rejection, KMZ-with-no-KML rejection

client/src/i18n/translations/cs.ts

@@ -1,4 +1,4 @@
-const cs: Record<string, string | { name: string; category: string }[]> = {
+const cs: Record<string, string | { name: string; category: string }[]> = {
   // Společné (Common)
   'common.save': 'Uložit',
   'common.showMore': 'Zobrazit více',