fix: harden update pipeline and restore a clean production build

- update-Nitrov3.sh: build CMS into .next-staging and swap atomically so a
  failed build never takes the live site down; auto-merge new variables
  from .env.example; validate env for duplicates/broken lines; restart the
  emulator/CMS only when rebuilt or unhealthy; fix step renumbering
- next.config.ts: support NEXT_DIST_DIR for staged production builds
- fix all TS errors (unused imports, missing tryDownloadCandidates helper)
  so tsc and the production build pass clean
- add Dockerfile/.dockerignore and switch docker-compose to a CMS container
- include prevailing UI/refactor changes (SurfaceCard, ticketing, tsconfig)

src/lib/services/soundtracks.ts

@@ -139,9 +139,4 @@ export type { TraxChannel, TraxEvent } from "@/lib/trax-format";
 // Re-export the Trax format parser for server-side use. The actual
 // implementation lives in `@/lib/trax-format` so it can be imported by
 // client components without pulling in Node-only deps from this file.
-export {
-	detectSoundtrackKind,
-	parseTrackSamples,
-	parseTraxChannels,
-	TRAX_TICK_SECONDS,
-} from "@/lib/trax-format";
+export { parseTrackSamples } from "@/lib/trax-format";