GSMTAP: --gsmtap-bind to listen beyond loopback (containers)

A container's 127.0.0.1 is its own loopback, so a GSMTAP feed sent to the
container's bridge address never reached the listener: it was hard-bound to
127.0.0.1.

- `simtrace-analyser-server --gsmtap-bind ADDR` (default 127.0.0.1) is passed
  through GsmtapListener to GsmtapReceiver (whose bind_ip already existed),
  including the receiver re-created by a start() after close.  The startup
  banner prints the effective bind address next to the port.
- READMEs (EN/RU) document the option, naming the container case.
- tests: the listener forwards the address on construction and on start(),
  binds 0.0.0.0, and keeps the loopback default.

Verified end-to-end: with --gsmtap-bind 0.0.0.0 the socket listens on
0.0.0.0:14732 and an ATR + APDU sent to 127.0.0.1:14732 landed in the capture
session (2 messages); without the flag it listens on 127.0.0.1.
557 Python + 80 Node tests.

tests/test_capture.py

@@ -206,6 +206,41 @@ class TestGsmtapListenerRobustness(unittest.TestCase):
         self.assertEqual(listener.dropped, 1)
 
 
+class TestGsmtapListenerBind(unittest.TestCase):
+    def test_bind_ip_reaches_the_receiver(self):
+        from simtrace_analyser import capture
+        calls = []
+
+        class _FakeReceiver:
+            def __init__(self, bind_ip='127.0.0.1', bind_port=4729):
+                calls.append((bind_ip, bind_port))
+
+            def close(self):
+                pass
+
+        real = capture.GsmtapReceiver
+        capture.GsmtapReceiver = _FakeReceiver
+        try:
+            listener = capture.GsmtapListener(bind_ip='0.0.0.0', bind_port=4729)
+            listener._receiver._closed = True  # force start() to re-create it
+            listener.start()
+        finally:
+            capture.GsmtapReceiver = real
+        self.assertEqual(calls, [('0.0.0.0', 4729), ('0.0.0.0', 4729)])
+
+    def test_all_interfaces_bind(self):
+        from simtrace_analyser.capture import GsmtapListener
+        listener = GsmtapListener(bind_ip='0.0.0.0', bind_port=0)
+        self.addCleanup(listener.stop)
+        self.assertEqual(listener._receiver._sock.getsockname()[0], '0.0.0.0')
+
+    def test_default_bind_is_loopback(self):
+        from simtrace_analyser.capture import GsmtapListener
+        listener = GsmtapListener(bind_port=0)
+        self.addCleanup(listener.stop)
+        self.assertEqual(listener._receiver._sock.getsockname()[0], '127.0.0.1')
+
+
 class TestCaptureLoopRobustness(unittest.TestCase):
     def test_capture_loop_survives_insert_error(self):
         mgr = CaptureManager(_OneShotBackend(), _NullDb())