Round every heading readout through one shared helper

The transit, ALPR, vessel, CCTV and flight/military context fixes each
wrapped 359.5° to north with an inline Math.round(x) % 360. They now call
roundHeadingDegrees in src/data/headingDegrees.js, which also wraps negative
and multi-turn bearings. normalizeHeading moves there with it, and
cockpitMath re-exports it so existing imports keep working. It now adds a
turn only to a negative remainder, so a bearing just under half a degree
keeps its precision.

The awareness, Local ADS-B, cockpit wind, cockpit heading and Street Level
readouts use the same helper. The Cockpit's TRACK ACQUIRED signal rounded
without wrapping and could read COURSE 360°; it now uses
formatHeadingReadout, which shows --- for a track that is not finite.

src/layers/cctv/headingConfidence.js

@@ -1,4 +1,5 @@
 import { t } from '../../i18n/index.js';
+import { roundHeadingDegrees } from '../../data/headingDegrees.js';
 
 /**
  * @module headingConfidence
@@ -44,8 +45,7 @@ export function isHeadingEstimated(camera) {
  * @returns {string}
  */
 export function headingHudToken(camera) {
-  // 359.5° and above rounds to north; modulo keeps it from printing 360°.
-  const hdg = Math.round(Number(camera?.headingDeg) || 0) % 360;
+  const hdg = roundHeadingDegrees(Number(camera?.headingDeg)) ?? 0;
   return isHeadingEstimated(camera)
     ? t('HDG {value}° (ESTIMATED)', { value: hdg })
     : t('HDG {value}°', { value: hdg });