- Add app/services/lemmy/discovery.py: searches 5 major Lemmy instances,
deduplicates by actor_id (AP canonical URL), skips NSFW communities,
uses community@instance naming convention matching existing Lemmy client
- Update POST /subs/discover: accepts platforms[] param (default both),
fans out to Reddit + Lemmy search, merges and sorts by subscribers
- Add platform field to all discovery result dicts (Reddit and Lemmy)
- Fix: remove dead _get() call left in search_subs() during earlier refactor
- Frontend: show platform badge on each discovery row, correct hyperlink
format for Lemmy (https://{instance}/c/{community}), pass r.platform
to upsertRules on import so Lemmy subs land in the lemmy platform slot