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/figuredata.ts

@@ -25,10 +25,7 @@ interface FigureDataFile {
 	setTypes: FdSetType[];
 }
 
-let pathOverride: string | null = null;
-export function __setFigureDataPathForTests(p: string | null): void {
-	pathOverride = p;
-}
+const pathOverride: string | null = null;
 
 export async function getFigureDataPath(): Promise<string> {
 	if (pathOverride) return pathOverride;