feat: GSMTAP-SIM APDU streaming for Wireshark / SIMtrace Analyser (v3.1.0)

Streams every APDU the server sends or receives as GSMTAP-SIM UDP packets,
so a live capture can be followed in Wireshark or the SIMtrace Analyser
without a hardware sniffer.  CLI-only: --gsmtap [HOST[:PORT]], default
target 127.0.0.1:4729; no UI or API.

- pysim_simple_server/gsmtap.py: 16-byte big-endian GSMTAP-SIM header
  (type 0x04, sub_type 0x00 = APDU / 0x01 = ATR) + raw APDU bytes, a
  fire-and-forget non-blocking sender that never raises into card I/O, an
  ApduTracer (a response is sent as data + SW1SW2, the wire form) and a
  fan-out tracer.  The packet layout is byte-identical to
  sigrok-iso7816-stream / simtrace2-sniff (verified against the sigrok
  module) and is what the analyser's GSMTAP receiver expects.
- __main__.py: --gsmtap option, tracer installed on the shared transport
  before the first APDU, combined with --apdu-trace via the fan-out and
  re-attached across equips (pySim nulls the tracer on every equip); one
  ATR packet per equip from _apply_equipped_card/_send_gsmtap_atr.
- start.sh/start.bat: forward their extra arguments to the server, so
  ./start.sh --gsmtap works.
- tests: packet layout, loopback UDP delivery, tracer mapping, target
  parsing, fan-out; docs (READMEs, help EN/RU, AGENTS); version 3.1.0,
  sw.js simple-v235.

frontend/index.html

@@ -1436,7 +1436,7 @@
 // ===== Version =====
 // Single source of truth for the PWA version: shown in the header and used
 // by the server version check in pysimConnect().
-const SIMPLE_VERSION = '3.0.1';
+const SIMPLE_VERSION = '3.1.0';
 document.getElementById('app-version').textContent = 'v' + SIMPLE_VERSION;
 
 // ===== Tab switching =====