feat: add rtl_tcp remote SDR support to weather satellite decoder

Extends the rtl_tcp support (added in c1339b6 for APRS, Morse, DSC) to
the weather satellite mode. When a remote SDR host is provided, SatDump
uses --source rtltcp instead of --source rtlsdr, local device claiming
is skipped, and the frontend sends rtl_tcp params via getRemoteSDRConfig().

Closes #166

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/test_weather_sat_decoder.py

@@ -136,6 +136,68 @@ class TestWeatherSatDecoder:
             assert 'noaa_apt' in cmd
             assert '--bias' in cmd
 
+    @patch('subprocess.Popen')
+    @patch('pty.openpty')
+    @patch('utils.weather_sat.register_process')
+    def test_start_rtl_tcp_uses_rtltcp_source(self, mock_register, mock_pty, mock_popen):
+        """start() with rtl_tcp should use --source rtltcp instead of rtlsdr."""
+        with patch('shutil.which', return_value='/usr/bin/satdump'):
+            mock_pty.return_value = (10, 11)
+            mock_process = MagicMock()
+            mock_process.poll.return_value = None
+            mock_popen.return_value = mock_process
+
+            decoder = WeatherSatDecoder()
+            callback = MagicMock()
+            decoder.set_callback(callback)
+
+            success, error_msg = decoder.start(
+                satellite='NOAA-18',
+                device_index=0,
+                gain=40.0,
+                rtl_tcp_host='192.168.1.100',
+                rtl_tcp_port=1234,
+            )
+
+            assert success is True
+            assert error_msg is None
+
+            mock_popen.assert_called_once()
+            cmd = mock_popen.call_args[0][0]
+            assert '--source' in cmd
+            source_idx = cmd.index('--source')
+            assert cmd[source_idx + 1] == 'rtltcp'
+            assert '--ip_address' in cmd
+            assert '192.168.1.100' in cmd
+            assert '--port' in cmd
+            assert '1234' in cmd
+            # Should NOT have --source_id for remote
+            assert '--source_id' not in cmd
+
+    @patch('subprocess.Popen')
+    @patch('pty.openpty')
+    @patch('utils.weather_sat.register_process')
+    def test_start_rtl_tcp_skips_device_resolve(self, mock_register, mock_pty, mock_popen):
+        """start() with rtl_tcp should skip _resolve_device_id."""
+        with patch('shutil.which', return_value='/usr/bin/satdump'), \
+             patch('utils.weather_sat.WeatherSatDecoder._resolve_device_id') as mock_resolve:
+            mock_pty.return_value = (10, 11)
+            mock_process = MagicMock()
+            mock_process.poll.return_value = None
+            mock_popen.return_value = mock_process
+
+            decoder = WeatherSatDecoder()
+
+            success, _ = decoder.start(
+                satellite='NOAA-18',
+                device_index=0,
+                gain=40.0,
+                rtl_tcp_host='10.0.0.1',
+            )
+
+            assert success is True
+            mock_resolve.assert_not_called()
+
     @patch('subprocess.Popen')
     @patch('pty.openpty')
     def test_start_already_running(self, mock_pty, mock_popen):

tests/test_weather_sat_routes.py

@@ -226,6 +226,68 @@ class TestWeatherSatRoutes:
             assert data['error_type'] == 'DEVICE_BUSY'
             assert 'Device busy' in data['message']
 
+    def test_start_capture_rtl_tcp_success(self, client):
+        """POST /weather-sat/start with rtl_tcp remote SDR."""
+        with patch('routes.weather_sat.is_weather_sat_available', return_value=True), \
+             patch('routes.weather_sat.get_weather_sat_decoder') as mock_get, \
+             patch('app.claim_sdr_device') as mock_claim:
+
+            mock_decoder = MagicMock()
+            mock_decoder.is_running = False
+            mock_decoder.start.return_value = (True, None)
+            mock_get.return_value = mock_decoder
+
+            payload = {
+                'satellite': 'NOAA-18',
+                'device': 0,
+                'gain': 40.0,
+                'rtl_tcp_host': '192.168.1.100',
+                'rtl_tcp_port': 1234,
+            }
+
+            response = client.post(
+                '/weather-sat/start',
+                data=json.dumps(payload),
+                content_type='application/json'
+            )
+
+            assert response.status_code == 200
+            data = response.get_json()
+            assert data['status'] == 'started'
+
+            # Device claim should NOT be called for remote SDR
+            mock_claim.assert_not_called()
+
+            # Verify rtl_tcp params passed to decoder
+            mock_decoder.start.assert_called_once()
+            call_kwargs = mock_decoder.start.call_args
+            assert call_kwargs[1]['rtl_tcp_host'] == '192.168.1.100'
+            assert call_kwargs[1]['rtl_tcp_port'] == 1234
+
+    def test_start_capture_rtl_tcp_invalid_host(self, client):
+        """POST /weather-sat/start with invalid rtl_tcp host."""
+        with patch('routes.weather_sat.is_weather_sat_available', return_value=True), \
+             patch('routes.weather_sat.get_weather_sat_decoder') as mock_get:
+
+            mock_decoder = MagicMock()
+            mock_decoder.is_running = False
+            mock_get.return_value = mock_decoder
+
+            payload = {
+                'satellite': 'NOAA-18',
+                'rtl_tcp_host': 'not a valid host!@#',
+            }
+
+            response = client.post(
+                '/weather-sat/start',
+                data=json.dumps(payload),
+                content_type='application/json'
+            )
+
+            assert response.status_code == 400
+            data = response.get_json()
+            assert data['status'] == 'error'
+
     def test_start_capture_start_failure(self, client):
         """POST /weather-sat/start when decoder.start() fails."""
         with patch('routes.weather_sat.is_weather_sat_available', return_value=True), \