Show absolute wall-clock time in the APDU detail heading

Next to the relative elapsed time, the detail-view header now shows
the absolute local time (YYYY-MM-DD HH:MM:SS.mmm) computed as
session start + message elapsed offset.

- STATE.sessionStarted populated from /api/capture/start (live
  capture), data.session.started (session view), and PCAP imports
  (sessions.started already derives from the first packet timestamp
  when real).
- Graceful fallback to relative-only when the session start is
  unknown; applies to all detail header variants (gap, no-decoded,
  state change, Fi/Di, ATR/PPS, APDU).

Version 1.17.0, SW cache simtrace-analyser-v24.

tests/test_pcap_import.py

@@ -197,7 +197,7 @@ class TestImportEndpoint(unittest.TestCase):
 class TestVersion(unittest.TestCase):
     def test_package_version(self):
         from simtrace2_pysniff import __version__
-        self.assertEqual(__version__, '1.16.1')
+        self.assertEqual(__version__, '1.17.0')
 
     def test_status_includes_version(self):
         import os