server+ui: detect card removal passively and reflect it within 2s

The UI only noticed a removed card when some user action ran a real card
command (e.g. Check status); /api/status is a cached-state read that kept
returning the old card, and _handle_card_disconnect() did not clear
app.card/rs.

- start_card_monitor() registers a pyscard CardObserver for our reader;
  it only polls SCardGetStatusChange (no APDU, no connection, no extra
  process), and on removal sets server.card_present=False and calls
  _handle_card_disconnect() under _CARD_LOCK
- /api/status now exposes connected (session usable) and card_present
  (physically inserted) and masks card/profile/atr/selection when not
  connected; _CARD_CONNECTED is initialized from card presence instead of
  being unconditionally True
- the 2s UI poll includes /api/status; on disconnect it switches to the
  existing 'No card detected. Insert card and click Equip' state, or the
  new 'Card inserted — press Equip' hint when the card is back; the old
  _hadData heuristic is gone

Tests for the observer (filtering, removal, insertion) and the UI state
transitions. SW cache v90 -> v91.

tests/test_card_monitor.py

@@ -0,0 +1,62 @@
+#!/usr/bin/env python3
+"""Tests for the passive PC/SC card-presence observer."""
+
+import sys
+import types
+import unittest
+from pathlib import Path
+from unittest import mock
+
+PROJECTS = Path(__file__).resolve().parents[2]
+PY_SIM = PROJECTS / 'pysim'
+if str(PY_SIM) not in sys.path:
+    sys.path.insert(0, str(PY_SIM))
+
+import pysim_otaman_server.server as S
+
+
+class FakeCard:
+    def __init__(self, reader):
+        self.reader = reader
+
+
+class TestCardPresenceObserver(unittest.TestCase):
+    def setUp(self):
+        self.observer = S._CardPresenceObserver('Test Reader 00 00')
+        self.server = types.SimpleNamespace(card_present=True)
+        self.saved_ref = S._server_ref
+        S._server_ref = self.server
+        self.disconnects = []
+        self.patcher = mock.patch.object(
+            S, '_handle_card_disconnect',
+            side_effect=lambda: self.disconnects.append(True))
+        self.patcher.start()
+
+    def tearDown(self):
+        self.patcher.stop()
+        S._server_ref = self.saved_ref
+
+    def test_removal_of_our_reader_disconnects(self):
+        self.observer.update(None, ([], [FakeCard('Test Reader 00 00')]))
+        self.assertFalse(self.server.card_present)
+        self.assertEqual(len(self.disconnects), 1)
+
+    def test_removal_of_other_reader_ignored(self):
+        self.observer.update(None, ([], [FakeCard('Other Reader 00 00')]))
+        self.assertTrue(self.server.card_present)
+        self.assertEqual(self.disconnects, [])
+
+    def test_insertion_sets_card_present(self):
+        self.server.card_present = False
+        self.observer.update(None, ([FakeCard('Test Reader 00 00')], []))
+        self.assertTrue(self.server.card_present)
+        self.assertEqual(self.disconnects, [])
+
+    def test_missing_reader_attribute_is_ignored(self):
+        self.observer.update(None, ([], [types.SimpleNamespace()]))
+        self.assertTrue(self.server.card_present)
+        self.assertEqual(self.disconnects, [])
+
+
+if __name__ == '__main__':
+    unittest.main()