Add rtl_tcp (remote SDR) support v1.1.0

Features:
- Add rtl_tcp support for pager and sensor decoding
  - Connect to remote RTL-SDR via rtl_tcp server
  - New UI toggle and host:port inputs in sidebar
  - Supports rtl_fm and rtl_433 with remote devices

- Add remote dump1090 support for ADS-B tracking
  - Connect to dump1090 SBS output on remote machine
  - New "Remote" checkbox with host:port in ADS-B dashboard

Backend changes:
- Add rtl_tcp_host/port fields to SDRDevice dataclass
- Add is_network property for detecting remote devices
- Update RTLSDRCommandBuilder to use rtl_tcp:host:port format
- Add create_network_device() to SDRFactory
- Add validate_rtl_tcp_host/port validation functions
- Update pager, sensor, and adsb routes to accept remote params

Note: dump1090 doesn't support rtl_tcp directly - use remote
dump1090's SBS output (port 30003) for remote ADS-B tracking.

utils/sdr/__init__.py

@@ -172,6 +172,34 @@ class SDRFactory:
             capabilities=caps
         )
 
+    @classmethod
+    def create_network_device(
+        cls,
+        host: str,
+        port: int = 1234
+    ) -> SDRDevice:
+        """
+        Create a network device for rtl_tcp connection.
+
+        Args:
+            host: rtl_tcp server hostname or IP address
+            port: rtl_tcp server port (default 1234)
+
+        Returns:
+            SDRDevice configured for rtl_tcp connection
+        """
+        caps = cls.get_capabilities(SDRType.RTL_SDR)
+        return SDRDevice(
+            sdr_type=SDRType.RTL_SDR,
+            index=0,
+            name=f'{host}:{port}',
+            serial='rtl_tcp',
+            driver='rtl_tcp',
+            capabilities=caps,
+            rtl_tcp_host=host,
+            rtl_tcp_port=port
+        )
+
 
 # Export commonly used items at package level
 __all__ = [

utils/sdr/base.py

@@ -46,15 +46,23 @@ class SDRDevice:
     serial: str
     driver: str                  # e.g., "rtlsdr", "lime", "hackrf"
     capabilities: SDRCapabilities
+    rtl_tcp_host: Optional[str] = None   # Remote rtl_tcp server host
+    rtl_tcp_port: Optional[int] = None   # Remote rtl_tcp server port
+
+    @property
+    def is_network(self) -> bool:
+        """Check if this is a network/remote device."""
+        return self.rtl_tcp_host is not None
 
     def to_dict(self) -> dict:
         """Convert to dictionary for JSON serialization."""
-        return {
+        result = {
             'index': self.index,
             'name': self.name,
             'serial': self.serial,
             'sdr_type': self.sdr_type.value,
             'driver': self.driver,
+            'is_network': self.is_network,
             'capabilities': {
                 'freq_min_mhz': self.capabilities.freq_min_mhz,
                 'freq_max_mhz': self.capabilities.freq_max_mhz,
@@ -66,6 +74,10 @@ class SDRDevice:
                 'tx_capable': self.capabilities.tx_capable,
             }
         }
+        if self.is_network:
+            result['rtl_tcp_host'] = self.rtl_tcp_host
+            result['rtl_tcp_port'] = self.rtl_tcp_port
+        return result
 
 
 class CommandBuilder(ABC):

utils/sdr/rtlsdr.py

@@ -27,6 +27,16 @@ class RTLSDRCommandBuilder(CommandBuilder):
         tx_capable=False
     )
 
+    def _get_device_arg(self, device: SDRDevice) -> str:
+        """Get device argument for rtl_* tools.
+
+        Returns rtl_tcp connection string for network devices,
+        or device index for local devices.
+        """
+        if device.is_network:
+            return f"rtl_tcp:{device.rtl_tcp_host}:{device.rtl_tcp_port}"
+        return str(device.index)
+
     def build_fm_demod_command(
         self,
         device: SDRDevice,
@@ -40,11 +50,11 @@ class RTLSDRCommandBuilder(CommandBuilder):
         """
         Build rtl_fm command for FM demodulation.
 
-        Used for pager decoding.
+        Used for pager decoding. Supports local devices and rtl_tcp connections.
         """
         cmd = [
             'rtl_fm',
-            '-d', str(device.index),
+            '-d', self._get_device_arg(device),
             '-f', f'{frequency_mhz}M',
             '-M', modulation,
             '-s', str(sample_rate),
@@ -73,7 +83,17 @@ class RTLSDRCommandBuilder(CommandBuilder):
         Build dump1090 command for ADS-B decoding.
 
         Uses dump1090 with network output for SBS data streaming.
+
+        Note: dump1090 does not support rtl_tcp. For remote SDR, connect to
+        a remote dump1090's SBS output (port 30003) instead.
         """
+        if device.is_network:
+            raise ValueError(
+                "dump1090 does not support rtl_tcp. "
+                "For remote ADS-B, run dump1090 on the remote machine and "
+                "connect to its SBS output (port 30003)."
+            )
+
         cmd = [
             'dump1090',
             '--net',
@@ -96,11 +116,11 @@ class RTLSDRCommandBuilder(CommandBuilder):
         """
         Build rtl_433 command for ISM band sensor decoding.
 
-        Outputs JSON for easy parsing.
+        Outputs JSON for easy parsing. Supports local devices and rtl_tcp connections.
         """
         cmd = [
             'rtl_433',
-            '-d', str(device.index),
+            '-d', self._get_device_arg(device),
             '-f', f'{frequency_mhz}M',
             '-F', 'json'
         ]