fix: cross-node gate decryption, UI text scaling, aircraft zoom

- Derive gate envelope AES key from gate ID via HKDF so all nodes
  sharing a gate can decrypt each other's messages (was node-local)
- Preserve gate_envelope/reply_to in chain payload normalization
- Bump Wormhole modal text from 9-10px to 12-13px
- Add aircraft icon zoom interpolation (0.8→2.0 across zoom 5-12)
- Reduce Mesh Chat panel text sizes for tighter layout

frontend/src/components/map/MapMarkers.tsx

@@ -106,7 +106,7 @@ export function TrackedFlightLabels({
               style={{
                 ...LABEL_BASE,
                 color: labelColor,
-                fontSize: '10px',
+                fontSize: `${Math.max(10, Math.min(16, 10 + (zoom - 5) * 1.2))}px`,
                 textShadow: LABEL_SHADOW_EXTRA,
                 whiteSpace: 'nowrap',
               }}
@@ -212,9 +212,11 @@ export function TrackedYachtLabels({ ships, inView, interpShip }: TrackedYachtLa
 interface UavLabelsProps {
   uavs: UAV[];
   inView: (lat: number, lng: number) => boolean;
+  zoom?: number;
 }
 
-export function UavLabels({ uavs, inView }: UavLabelsProps) {
+export function UavLabels({ uavs, inView, zoom = 5 }: UavLabelsProps) {
+  const labelSize = `${Math.max(10, Math.min(16, 10 + (zoom - 5) * 1.2))}px`;
   return (
     <>
       {uavs.map((uav, i) => {
@@ -234,7 +236,7 @@ export function UavLabels({ uavs, inView }: UavLabelsProps) {
               style={{
                 ...LABEL_BASE,
                 color: '#ff8c00',
-                fontSize: '10px',
+                fontSize: labelSize,
                 textShadow: LABEL_SHADOW_EXTRA,
                 whiteSpace: 'nowrap',
               }}