Map: TRAFFIC (TCAS) + NEXRAD overlays — two more dead softkeys now functional

The TRAFFIC and NEXRAD map keys were dead. Now: TRAFFIC draws TCAS diamonds
(threat-coloured other/proximate/TA/RA, relative altitude + climb/descend arrow);
NEXRAD draws green/yellow/red precip cells. Both toggle from the MAP softkeys and
light when active. Driven by values.traffic / values.wxCells, which the demo
synthesizes so they're demonstrable; the live-sim binding (TCAS/weather datarefs)
is the part that still needs a sim session to wire+verify.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/bridge.js

@@ -326,6 +326,17 @@ function startDemo() {
     engRpm: [2410], fuelFlow: [0.0072], oilTemp: [88], oilPress: [52], egt: [720],
     fuelQty: [60, 58], volts: [process.env.DEMO_ALERT ? 23.4 : 28.0, 27.8], amps: [-1.5], genAmps: [20.5], engHrs: 5040,
     fuelTot: 118 * 2.72, fuelMax: 144 * 2.72, // fuel totalizer: 118 of 144 gal (kg) — SYSTEM keys adjust
+    // TRAFFIC (TCAS) + NEXRAD demo data so those map overlays are demonstrable.
+    // relAlt = hundreds of ft vs own ship; vs +/- = climb/descend; thr = TA/RA.
+    traffic: [
+      { lat: 47.52, lon: -122.28, relAlt: 12, vs: 1, thr: 0 },
+      { lat: 47.40, lon: -122.45, relAlt: -8, vs: -1, thr: 1 },
+      { lat: 47.47, lon: -122.18, relAlt: 2, vs: 0, thr: 2 },
+    ],
+    wxCells: [ // synthetic NEXRAD precip: lat,lon,radiusNm,level(1 green·2 yellow·3 red)
+      { lat: 47.7, lon: -122.0, r: 8, lvl: 2 }, { lat: 47.75, lon: -121.9, r: 5, lvl: 3 },
+      { lat: 47.2, lon: -122.6, r: 10, lvl: 1 }, { lat: 47.25, lon: -122.5, r: 6, lvl: 2 },
+    ],
   });
   // a sample plan so the map/FMS show something in demo mode
   fp.setPlan({ name: 'DEMO', waypoints: [