Decode sigrok-iso7816-stream RST/VCC line events (GSMTAP 0x10/0x11)

Support the sigrok-iso7816-stream decoder (FX2 logic-analyzer passive
SIM sniffer, github.com/anttro/sigrok_iso7816_stream) which streams
GSMTAP-SIM on UDP 4729 and adds two custom sub-types for line events.

- gsmtap.py: GSMTAP_SIM_RST_EVENT (0x10) / GSMTAP_SIM_VCC_EVENT (0x11).
- capture.py: gsmtap_msg_type() maps 0x10→'rst', 0x11→'vcc' (shared by
  the listener and tests); pcap.py _SUB_TYPE_NAMES gains the same
  entries so PCAP re-imports of these captures preserve the events.
- decode.py: decode_line_event() decodes [direction, level, reserved]
  into reset asserted/de-asserted or power applied/removed + level;
  routed through decode_sniff_msg.
- database.py: reset-assert and power-removal invalidate the per-channel
  file selection (card-level transition); de-assert / power-on are
  markers only.
- frontend: RST/VCC labels (RESET ASSERTED / VCC OFF, …), a detail-view
  branch (Event + Level + raw), and list styling (.apdu-type.rst/.vcc).

README notes the custom sub-type compatibility. Tests: +8 (line-event
vectors, sniff routing, subtype + PCAP round-trip mappings) — 359
total. Version 1.21.0, SW cache simtrace-analyser-v31.

tests/test_capture.py

@@ -4,10 +4,21 @@ import os
 import tempfile
 import unittest
 
-from simtrace2_pysniff.server.capture import CaptureManager
+from simtrace2_pysniff.server.capture import CaptureManager, gsmtap_msg_type
 from simtrace2_pysniff.server.database import Database
 
 
+class TestGsmtapSubtypeMapping(unittest.TestCase):
+    def test_custom_line_event_subtypes(self):
+        self.assertEqual(gsmtap_msg_type(0x10), 'rst')
+        self.assertEqual(gsmtap_msg_type(0x11), 'vcc')
+
+    def test_standard_subtypes(self):
+        self.assertEqual(gsmtap_msg_type(0x00), 'tpdu')
+        self.assertEqual(gsmtap_msg_type(0x01), 'atr')
+        self.assertEqual(gsmtap_msg_type(0x02), 'tpdu')  # PPS combined
+
+
 class _FakeBackend:
     def __init__(self, messages=()):
         self._messages = list(messages)