Phase 3: J-IDs, ownership, roles, guest safety, adaptive detail, download

Backend:
- User.role (user/uploader/staff) with can_upload; uploads and downloads
  gated to uploader+; owners and staff can edit their items
- MediaItem.uploaded_by plus J-<id> identity (serializer, admin,
  scan_files --user, first superuser as default owner)
- API resolves J-<id>, bare numeric ids and MD5s; neighbors and lookup
  return j_ids
- Guest safety: mirror e621's anonymous default blacklist into Redis
  (parses comments, negations and wildcards), flag hidden_from_guests
  and filter lists, details and lookups for anonymous users
- POST /api/online/downloads/ writes an e621 file into the watched
  folder and indexes it for the uploader
- MariaDB + Redis via docker compose (host ports 3307/6380), PyMySQL
  driver shim, Redis cache replacing the file cache; SQLite data
  dumped and loaded into MariaDB

Frontend:
- Single /detail/:itemId route with an adaptive shell: J-<id> renders
  the library item, bare numbers render the e621 post
- Legacy /view/<md5> and /online/view/<id> redirect to canonical URLs
- Cards expose J-IDs; library custom-data editor is read-only for
  non-owners
- Role gating: Upload hidden/blocked for regular users, account shows
  the role, guest hint on the library

backend/.env.example

@@ -3,3 +3,18 @@ DEBUG=True
 ALLOWED_HOSTS=localhost,127.0.0.1
 # Absolute path to your media folder, or relative to the backend/ folder.
 WATCHED_FOLDER=media/library
+
+# MariaDB (docker compose at the repo root)
+DB_HOST=127.0.0.1
+DB_PORT=3307
+DB_NAME=j621
+DB_USER=j621
+DB_PASSWORD=j621
+
+# Redis (docker compose at the repo root)
+REDIS_URL=redis://127.0.0.1:6380/1
+
+# Guest visibility: e621's anonymous default blacklist is mirrored into
+# Redis by `manage.py refresh_guest_blacklist`.
+# GUEST_BLACKLIST_FALLBACK=young,cub,shota,loli,child,underage
+# GUEST_BLACKLIST_TTL=3600