Add Starlink status lines for the physical gateway pane (closes #3)

When the non-VPN physical gateway is a Starlink dish, two lines are shown
under that pane: state, uptime, obstruction and alert count; then pop-ping
latency and drop rate with downlink/uplink throughput. They turn red when
the dish is not connected or an alert is active.

Detection is a TCP connect to the dish's fixed endpoint 192.168.100.1:9200,
bound to the physical interface the same way the latency probes bind. Until
a dish answers nothing is drawn and no status is fetched, so an absent dish
adds no noise. Status comes from the dish's local get_status gRPC call.

Detection and the fetch sit behind a small Client interface; the loop and
the pure Render function are tested with a fake, no dish and no network.

Model: opus-4-8

internal/monitor/monitor.go

@@ -19,6 +19,8 @@ import (
 	"time"
 
 	tcell "github.com/gdamore/tcell/v2"
+
+	"git.eeqj.de/sneak/rtnetmon/internal/starlink"
 )
 
 // Meter glyphs used to render the ASCII loss meter.
@@ -90,6 +92,12 @@ type Monitor struct {
 	// Interfaces to monitor (one or two)
 	interfaces []*InterfaceStatus
 
+	// Starlink status for the physical (non-VPN gateway) pane. All three
+	// are nil unless EnableStarlink was called for a monitored interface.
+	slClient starlink.Client
+	slState  *starlinkState
+	slPane   *InterfaceStatus
+
 	// Logging
 	logFile string
 
@@ -208,6 +216,8 @@ func (m *Monitor) Run(ctx context.Context) error {
 		go m.tcpLoop(ctx, st, tcpHosts)
 	}
 
+	go m.starlinkLoop(ctx)
+
 	m.logf("Starting UI loop")
 	m.uiLoop(ctx)
 	m.logf("UI loop exited, monitor ending")