Change details: no filler past a short file, no offsets for a single row (v2.7.3)

- the hex views padded every line to 16 bytes with '--', so a 2-byte file
  looked like it was missing data; the row now ends at the known file/record
  length (from the FCP — hexImageRows gained the size parameter), while '--'
  still marks bytes *inside* the file that were never observed (an unknown
  length keeps the old row padding, nothing better is available)
- the offset column is shown only when a view spans more than one row — a
  four-hex-digit 0000 above two bytes was noise
- the legend lists only the marks actually rendered: 'never observed' is gone
  from a short/fully-observed view, and 'newly observed' when nothing was
  first observed (the summary line still counts both)
- tests: pure hexImageRows cases (the 2-byte file, a 9-byte record with an
  unobserved tail, the unknown-size fallback) plus two renderFileDiff cases
  pinning the missing filler/offset and the trimmed legend; 527 Python +
  75 Node tests
- README/README_RUS describe the new hex-view behaviour;
  PWA_VERSION/pyproject/version.py 2.7.3, SW cache simtrace-analyser-v83

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.backends._legacy:_Backend"
 
 [project]
 name = "simtrace-analyser"
-version = "2.7.2"
+version = "2.7.3"
 description = "SIMtrace Analyser — APDU trace analyser for GSMTAP/PCAP captures (bundles the simtrace2-pysniff utility)"
 readme = {file = "README.md", content-type = "text/markdown"}
 license = {text = "GPL-2.0-or-later"}