chore: drop exports nothing imports

Knip, configured with the application, package exports, scripts, QA
harnesses, workers, tools and tests as entry points, reports exports
that no module imports. Each was checked by hand against string-based
and namespace imports.

- Symbols that are still used inside their own module lose only the
  `export` keyword (176 constants and helpers).
- Unused re-exports are removed from barrel modules (flight, military,
  vessel, CCTV, directions, transit history, local ADS-B and street-level
  policy modules).
- Declarations that nothing uses at all are deleted, among them
  AIS_WATCHDOG_STATUSES, applyFilter, isRadioCountryCode, compactText,
  DENSITY_STOPS, the unused CCTV endpoint constants, and the SDR band
  constants.
- Default exports that nothing imports are removed. The ones in
  src/data/earthquakes.js, src/data/telegeographySubmarineCables.js,
  src/data/wind.js and src/data/bhoteKoshiLocator.js each constructed a
  layer instance at import time that nothing used; those instances are
  no longer created.

Every export of a package.json entry stays, as does TOMTOM_CREDIT,
which the traffic layer reads from the credits namespace it is given.

src/annotations/drawMode.js

@@ -31,10 +31,10 @@ export const MIN_VERTICES = Object.freeze({ area: 3, line: 2, pin: 1 });
  */
 export const MAX_VERTICES = 512;
 /** Two clicks closer than this are one vertex: a double-click to finish must not add a stray point. */
-export const MIN_VERTEX_SEPARATION_M = 0.5;
+const MIN_VERTEX_SEPARATION_M = 0.5;
 /** A line shorter than this, or an area thinner than this, is a mis-click rather than a shape. */
-export const MIN_PATH_LENGTH_M = 1;
-export const MIN_AREA_M2 = 1;
+const MIN_PATH_LENGTH_M = 1;
+const MIN_AREA_M2 = 1;
 
 /** @param {string} shape @returns {'area'|'line'|'pin'} */
 export function normalizeShape(shape) {
@@ -50,7 +50,7 @@ export function createDrawSession(shape = 'area') {
 }
 
 /** Great-circle distance in metres between two {lon, lat} points. */
-export function greatCircleM(a, b) {
+function greatCircleM(a, b) {
   return greatCircleMeters(a, b);
 }