Add ONION-URLS.md, export script, and tighten README

- ONION-URLS.md: static registry of all 43 hidden services (port, role, app path)
- scripts/export-onion-urls.sh: writes live .onion addresses to onion-urls.txt at runtime
- npm run onions:export shortcut added to package.json
- onion-urls.txt added to .gitignore (runtime artifact, not source)
- README: cohesive rewrite — architecture diagram, operator command table, source-of-truth
  map, BTCPay notes, full site map, common fixes
- BTCPay status route: awaited params destructuring (Next 15 async params)

Made-with: Cursor

.gitignore

@@ -39,3 +39,6 @@ yarn-error.log*
 # typescript
 *.tsbuildinfo
 next-env.d.ts
+
+# runtime-generated onion URL file (populated by scripts/export-onion-urls.sh)
+onion-urls.txt