versioninfo: add JADE_INTERFACE field to show which connection source holds the unlocked wallet

### docs/index.rst
@@ -151,6 +151,7 @@ get_version_info reply
             "EFUSEMAC": "246F288F6364",
             "BATTERY_STATUS": 5,
             "JADE_STATE": "LOCKED",
+            "JADE_INTERFACE": "NONE",
             "JADE_NETWORKS': "MAIN",
             "JADE_HAS_PIN": true
         }
@@ -166,6 +167,14 @@ get_version_info reply
   - 'READY' - wallet set and unlocked for this interface, ready to use.
   - 'TEMP' - hw currently set with a temporary ('Emergency Restore') wallet, ready to use.
 
+* 'JADE_INTERFACE' : the connection interface which currently holds the unlocked wallet, if any.
+  While a wallet is held by one interface it cannot be used over another
+
+  - 'NONE' - wallet is not currently held by any connection interface (so can be unlocked)
+  - 'QR' - wallet is held by the on-device QR interface (eg. a temporary 'QR Mode' wallet)
+  - 'SERIAL' - wallet is held by the USB/serial connection
+  - 'BLE' - wallet is held by the Bluetooth connection
+
 * 'JADE_NETWORKS' :
 
   - 'MAIN' - wallet is locked to mainnet/production networks and cannot be used on testnet or regtest networks.

### main/versioninfo.c
@@ -24,6 +24,26 @@ extern esp_app_desc_t running_app_info;
 extern esp_chip_info_t chip_info;
 extern uint8_t macid[6];
 
+static const char* get_interface_name(const jade_msg_source_t source)
+{
+    switch (source) {
+    case SOURCE_INTERNAL:
+        return "QR";
+    case SOURCE_SERIAL:
+        return "SERIAL";
+    case SOURCE_QEMU_TCP:
+        return "QEMU_TCP";
+    case SOURCE_BLE:
+        return "BLE";
+#ifdef CONFIG_LIBJADE
+    case SOURCE_LIBJADE:
+        return "LIBJADE";
+#endif
+    default:
+        return "NONE";
+    }
+}
+
 void build_version_info_reply(const void* ctx, CborEncoder* container)
 {
     JADE_ASSERT(ctx);
@@ -32,9 +52,9 @@ void build_version_info_reply(const void* ctx, CborEncoder* container)
     const jade_msg_source_t* const source = (const jade_msg_source_t*)ctx;
 
 #ifdef CONFIG_DEBUG_MODE
-    const uint8_t num_version_fields = 22;
+    const uint8_t num_version_fields = 23;
 #else
-    const uint8_t num_version_fields = 15;
+    const uint8_t num_version_fields = 16;
 #endif
 
     CborEncoder map_encoder;
@@ -110,6 +130,10 @@ void build_version_info_reply(const void* ctx, CborEncoder* container)
         add_string_to_map(&map_encoder, "JADE_STATE", has_pin ? "LOCKED" : "UNINIT");
     }
 
+    // The connection interface which currently holds the (unlocked) wallet, if any.
+    // While a wallet is held by one interface it cannot be used over another
+    add_string_to_map(&map_encoder, "JADE_INTERFACE", get_interface_name((jade_msg_source_t)keychain_get_userdata()));
+
     const network_type_t restriction = keychain_get_network_type_restriction();
     const char* networks = restriction == NETWORK_TYPE_MAIN ? "MAIN"
         : restriction == NETWORK_TYPE_TEST                  ? "TEST"

### test_jade.py
@@ -176,7 +176,7 @@ def _get_test_cases(pattern, allow_sampling=True):
 STALE_DATA_TIMEOUT = 4
 
 # The number of values expected back in version info
-NUM_VALUES_VERINFO = 22
+NUM_VALUES_VERINFO = 23
 ESP32S3_CHIP_BOARDS = ['JADE_V2', 'JADE_V2C', 'TTGO_TDISPLAYS3', 'TTGO_TDISPLAYS3PROCAMERA',
                        'M5CORES3']
 

### tests/rpc/test_low_level.py
@@ -11,7 +11,7 @@
 # This value must be > TIMEOUT_TICKS to reliably trigger the stale path.
 STALE_DATA_TIMEOUT = 4
 
-NUM_VALUES_VERINFO = 22
+NUM_VALUES_VERINFO = 23
 
 LOW_LEVEL_VECTORS = next(_get_test_cases('tests/rpc/data/low_level/bad_params.json'))[0]
 LOW_LEVEL_LIQUID_VECTORS = next(_get_test_cases(

### tests/rpc/test_pin_actions.py
@@ -189,6 +189,34 @@ def test_pin_requires_auth_user(jade):
     assert reply['error']['message'] == 'Unexpected method'
 
 
+@pytest.mark.mnemonic(mnemonics.reset)
+def test_version_info_interface(pin_test_setup):
+    """Check 'JADE_INTERFACE' identifies the connection holding the unlocked wallet"""
+    jade, _, _ = pin_test_setup
+
+    config = get_jade_config()
+    if config.transport == 'ble':
+        expected_interface = 'BLE'
+    elif config.transport == 'libjade':
+        expected_interface = 'SERIAL'
+    elif config.device.startswith('tcp:'):
+        expected_interface = 'QEMU_TCP'
+    else:
+        expected_interface = 'SERIAL'
+
+    # The wallet is unlocked/held by this connection (pin_test_setup sets a pin and
+    # then calls auth_user)
+    info = jade.get_version_info()
+    assert info['JADE_STATE'] == 'READY'
+    assert info['JADE_INTERFACE'] == expected_interface
+
+    # Once logged out the wallet is no longer held by any connection
+    assert jade.logout() is True
+    info = jade.get_version_info()
+    assert info['JADE_STATE'] == 'LOCKED'
+    assert info['JADE_INTERFACE'] == 'NONE'
+
+
 @pytest.mark.mnemonic(mnemonics.reset)
 def test_bad_pin(pin_test_setup):
     """Check that Jade rejects bad PINs passed to 'debug_set_pin'"""

### tests/rpc/test_ping.py
@@ -1,7 +1,7 @@
 from . import *
 
 
-NUM_VALUES_VERINFO = 22
+NUM_VALUES_VERINFO = 23
 
 
 def test_ping_protocol(jade):