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.

server/providers/cctv/taiwan.js

@@ -12,14 +12,14 @@ export const TAIWAN_FREEWAY_CCTV_URL =
   'https://tisvcloud.freeway.gov.tw/history/motc20/CCTV.xml';
 /** The whole network is ~1.2 MB. */
 export const TAIWAN_MAX_CATALOG_BYTES = 6 * 1024 * 1024;
-export const DEFAULT_TAIWAN_MAX_SOURCES = 600;
+const DEFAULT_TAIWAN_MAX_SOURCES = 600;
 /** After a failed download, wait this long before asking again. The catalog
  * host does not answer from some networks outside Taiwan, and every attempt
  * there holds the shared catalog refresh until the connect timeout. */
 export const TAIWAN_RETRY_AFTER_FAILURE_MS = 60 * 60 * 1000;
 /** The table is republished daily; a good copy stands in for a failed
  * download for up to this long. */
-export const TAIWAN_LAST_GOOD_MAX_AGE_MS = 24 * 60 * 60 * 1000;
+const TAIWAN_LAST_GOOD_MAX_AGE_MS = 24 * 60 * 60 * 1000;
 
 // The table publishes each camera's MJPEG stream. The same camera servers
 // answer a single JPEG for the same camera ID on a sibling path, which is what
@@ -50,7 +50,7 @@ const ANCHORS = [
 
 /** Taiwan main island with slack for the coast; the freeway network has no
  * offshore-island cameras. */
-export function isLikelyTaiwanCoordinate(lat, lon) {
+function isLikelyTaiwanCoordinate(lat, lon) {
   return (
     Number.isFinite(lat) &&
     Number.isFinite(lon) &&