Add VRS JSON format support for readsb integration

Added comprehensive support for VRS (Virtual Radar Server) JSON format
as a simpler alternative to Beast binary protocol, enabling integration
with readsb --net-vrs-port output.

## Key Features:
- **VRS JSON Parser**: Stream parsing of newline-delimited JSON aircraft data
- **VRS Client**: TCP client with automatic reconnection and error recovery
- **Mixed Format Support**: Use Beast and VRS sources simultaneously
- **Enhanced Aircraft Data**: Added VRS-specific fields (registration, type, operator)
- **Position Source Tracking**: Identifies ADS-B, MLAT, TIS-B, and satellite positions

## Implementation:
- `internal/vrs/parser.go`: VRS JSON message parsing and validation
- `internal/client/vrs.go`: VRS TCP client implementation
- Enhanced `MultiSourceClient` to support both Beast and VRS formats
- Extended `Aircraft` struct with validity flags and additional metadata
- Updated configuration to include `format` field ("beast" or "vrs")

## Testing:
- Successfully tested against svovel:33005 VRS JSON stream
- Verified aircraft data parsing and position tracking
- Confirmed mixed-format operation with existing Beast clients

## Documentation:
- Updated README.md with VRS format configuration examples
- Enhanced ARCHITECTURE.md with VRS parser documentation
- Added data format comparison and configuration guide

This enables simpler integration with modern readsb installations while
maintaining full backward compatibility with existing Beast deployments.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

internal/client/beast.go

@@ -250,10 +250,10 @@ func (c *BeastClient) processMessages() {
 	}
 }
 
-// MultiSourceClient manages multiple Beast TCP clients for multi-receiver setups.
+// MultiSourceClient manages multiple Beast and VRS clients for multi-receiver setups.
 //
 // This client coordinator:
-//   - Manages connections to multiple Beast format sources simultaneously
+//   - Manages connections to multiple Beast and VRS format sources simultaneously
 //   - Provides unified control for starting and stopping all clients
 //   - Runs periodic cleanup tasks for stale aircraft data
 //   - Aggregates statistics from all managed clients
@@ -262,21 +262,23 @@ func (c *BeastClient) processMessages() {
 // All clients share the same data merger, enabling automatic data fusion
 // and conflict resolution across multiple receivers.
 type MultiSourceClient struct {
-	clients []*BeastClient // Managed Beast clients
-	merger  *merger.Merger // Shared data merger for all sources
-	mu      sync.RWMutex   // Protects clients slice
+	beastClients []*BeastClient // Managed Beast clients
+	vrsClients   []*VRSClient   // Managed VRS JSON clients
+	merger       *merger.Merger // Shared data merger for all sources
+	mu           sync.RWMutex   // Protects client slices
 }
 
-// NewMultiSourceClient creates a client manager for multiple Beast format sources.
+// NewMultiSourceClient creates a client manager for multiple Beast and VRS format sources.
 //
-// The multi-source client enables connecting to multiple dump1090 instances
-// or other Beast format sources simultaneously. All sources feed into the
-// same data merger, which handles automatic data fusion and conflict resolution.
+// The multi-source client enables connecting to multiple dump1090/readsb instances
+// using either Beast binary or VRS JSON formats simultaneously. All sources feed into
+// the same data merger, which handles automatic data fusion and conflict resolution.
 //
 // This is essential for:
 //   - Improved coverage from multiple receivers
 //   - Redundancy in case of individual receiver failures
 //   - Data quality improvement through signal strength comparison
+//   - Support for different receiver output formats
 //
 // Parameters:
 //   - merger: Shared data merger instance for all sources
@@ -284,18 +286,23 @@ type MultiSourceClient struct {
 // Returns a configured multi-source client ready for source addition.
 func NewMultiSourceClient(merger *merger.Merger) *MultiSourceClient {
 	return &MultiSourceClient{
-		clients: make([]*BeastClient, 0),
-		merger:  merger,
+		beastClients: make([]*BeastClient, 0),
+		vrsClients:   make([]*VRSClient, 0),
+		merger:       merger,
 	}
 }
 
-// AddSource registers and configures a new Beast format data source.
+// AddSource registers and configures a new data source (Beast or VRS format).
 //
 // This method:
 //  1. Registers the source with the data merger
-//  2. Creates a new BeastClient for the source
+//  2. Creates appropriate client based on source format
 //  3. Adds the client to the managed clients list
 //
+// The source format is determined by the source.Format field:
+//   - "beast": Creates a BeastClient for Beast binary protocol (default)
+//   - "vrs": Creates a VRSClient for VRS JSON protocol
+//
 // The source is not automatically started; call Start() to begin connections.
 // Sources can be added before or after starting the multi-source client.
 //
@@ -305,18 +312,31 @@ func (m *MultiSourceClient) AddSource(source *merger.Source) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 
+	// Default to Beast format if not specified
+	if source.Format == "" {
+		source.Format = "beast"
+	}
+
 	// Register source with merger
 	m.merger.AddSource(source)
 
-	// Create and start client
-	client := NewBeastClient(source, m.merger)
-	m.clients = append(m.clients, client)
+	// Create appropriate client based on format
+	switch source.Format {
+	case "vrs":
+		client := NewVRSClient(source, m.merger)
+		m.vrsClients = append(m.vrsClients, client)
+	case "beast":
+		fallthrough
+	default:
+		client := NewBeastClient(source, m.merger)
+		m.beastClients = append(m.beastClients, client)
+	}
 }
 
-// Start begins connections to all configured Beast sources.
+// Start begins connections to all configured sources (Beast and VRS).
 //
 // This method:
-//   - Starts all managed BeastClient instances in parallel
+//   - Starts all managed BeastClient and VRSClient instances in parallel
 //   - Begins the periodic cleanup routine for stale aircraft data
 //   - Uses the provided context for cancellation control
 //
@@ -330,7 +350,13 @@ func (m *MultiSourceClient) Start(ctx context.Context) {
 	m.mu.RLock()
 	defer m.mu.RUnlock()
 
-	for _, client := range m.clients {
+	// Start Beast clients
+	for _, client := range m.beastClients {
+		client.Start(ctx)
+	}
+
+	// Start VRS clients
+	for _, client := range m.vrsClients {
 		client.Start(ctx)
 	}
 
@@ -338,7 +364,7 @@ func (m *MultiSourceClient) Start(ctx context.Context) {
 	go m.cleanupRoutine(ctx)
 }
 
-// Stop gracefully shuts down all managed Beast clients.
+// Stop gracefully shuts down all managed clients (Beast and VRS).
 //
 // This method stops all clients in parallel and waits for their
 // goroutines to complete. The shutdown is coordinated to ensure
@@ -347,7 +373,13 @@ func (m *MultiSourceClient) Stop() {
 	m.mu.RLock()
 	defer m.mu.RUnlock()
 
-	for _, client := range m.clients {
+	// Stop Beast clients
+	for _, client := range m.beastClients {
+		client.Stop()
+	}
+
+	// Stop VRS clients
+	for _, client := range m.vrsClients {
 		client.Stop()
 	}
 }
@@ -382,8 +414,8 @@ func (m *MultiSourceClient) cleanupRoutine(ctx context.Context) {
 //
 // The statistics include:
 //   - All merger statistics (aircraft count, message rates, etc.)
-//   - Number of active client connections
-//   - Total number of configured clients
+//   - Number of active client connections (Beast and VRS)
+//   - Total number of configured clients by type
 //   - Per-source connection status and message counts
 //
 // This information is useful for monitoring system health, diagnosing
@@ -397,15 +429,26 @@ func (m *MultiSourceClient) GetStatistics() map[string]interface{} {
 	stats := m.merger.GetStatistics()
 
 	// Add client-specific stats
-	activeClients := 0
-	for _, client := range m.clients {
+	activeBeastClients := 0
+	for _, client := range m.beastClients {
 		if client.source.Active {
-			activeClients++
+			activeBeastClients++
 		}
 	}
 
-	stats["active_clients"] = activeClients
-	stats["total_clients"] = len(m.clients)
+	activeVRSClients := 0
+	for _, client := range m.vrsClients {
+		if client.source.Active {
+			activeVRSClients++
+		}
+	}
+
+	stats["active_beast_clients"] = activeBeastClients
+	stats["active_vrs_clients"] = activeVRSClients
+	stats["active_clients"] = activeBeastClients + activeVRSClients
+	stats["total_beast_clients"] = len(m.beastClients)
+	stats["total_vrs_clients"] = len(m.vrsClients)
+	stats["total_clients"] = len(m.beastClients) + len(m.vrsClients)
 
 	return stats
 }