WIP: Meteor 2.5 -> 3.1 migration (package resolution done; build blocked)

Reaches release METEOR@3.1 with all package-version conflicts resolved against a
modern dockerized MongoDB 7 (replica set). NOT yet building — parked here.

Done:
- MongoDB 7 single-node replica set (docker, port 27019) as the fuegos DB,
  decoupled from the shared rsmain 3.2 (unblocks Meteor 3's mongodb driver).
- meteor update --release 3.1 resolves after swapping dead packages:
  mongo-livedata removed; facts -> facts-base; saucecode:timezoned-synced-cron
  -> quave:synced-cron; aldeed:collection2-core -> aldeed:collection2@4.0.4;
  mys:fonts removed (pinned caching-compiler@1.0.0); fourseven:scss 4.14.1 ->
  5.0.0 (Dart Sass, no node-sass) + sass installed; nimble-restivus vendored
  package loosened to accounts-password 2.x||3.x.
- Network: meteor-tool node 22 needs NODE_OPTIONS='--dns-result-order=ipv4first
  --no-network-family-autoselection' to reach warehouse.meteor.com (Happy
  Eyeballs picks an unreachable IPv6 otherwise).
- smoke/smoke.sh generalized to mongosh + configurable port for Mongo 7.

Blocked on (remaining Meteor 3 work):
1. Client bundle linker: 'Runtime is not available, but it uses features needing
   the runtime: underscore' — an old client atmosphere package needs replacing.
2. Server async/await migration (Rest.js + helpers + methods + publications +
   comments + subsUnion + migrations to *Async; no Fibers).
3. Patch vendored restivus to await async endpoint handlers.
4. cron.js SyncedCron import (quave), facts.js Facts import (facts-base).
5. React 16 -> 18 render root (createRoot).
6. SCSS @import/@use + lighten/darken -> color.adjust (dart-sass deprecations).

package.json

@@ -99,7 +99,8 @@
     "eslint-plugin-jsx-a11y": "^6.0.2",
     "eslint-plugin-meteor": "^4.1.6",
     "eslint-plugin-react": "^7.4.0",
-    "jest": "^21.2.1"
+    "jest": "^21.2.1",
+    "sass": "^1.101.0"
   },
   "eslintConfig": {
     "parserOptions": {