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/data/geoFileImport.js

@@ -5,9 +5,9 @@ import { createImportedPins } from './geoImportPins.js';
 import { msg } from '../i18n/marker.js';
 
 /** Largest file accepted, in bytes. */
-export const MAX_IMPORT_BYTES = 50 * 1024 * 1024;
+const MAX_IMPORT_BYTES = 50 * 1024 * 1024;
 /** Largest total a KMZ may inflate to — a zip bomb stops here. */
-export const MAX_KMZ_INFLATED_BYTES = 120 * 1024 * 1024;
+const MAX_KMZ_INFLATED_BYTES = 120 * 1024 * 1024;
 /** Most files on the globe at once. */
 export const MAX_IMPORTED_FILES = 12;
 /** Most entities one file may create before it is refused. */
@@ -15,9 +15,9 @@ export const MAX_IMPORT_ENTITIES = 20_000;
 /** Most vertices (points of every line, ring and marker) in one file. */
 export const MAX_IMPORT_POSITIONS = 250_000;
 /** Most normalized style definitions and local image links in one KML/KMZ. */
-export const MAX_KML_LINKS = 2_000;
+const MAX_KML_LINKS = 2_000;
 /** Longest plain-text name kept from a file's features. */
-export const MAX_IMPORT_NAME_LENGTH = 120;
+const MAX_IMPORT_NAME_LENGTH = 120;
 /** What the file picker offers. */
 export const GEO_FILE_ACCEPT = '.geojson,.json,.kml,.kmz,.gpx';