Seed orchestrator: remote nodes lease ranges and post results over HTTPS

- seed_nodes (hashed bearer tokens) and seed_ranges (planned ranges with
  lease, resume point and counts); migration …140.
- SeedOrchestrator: lease (oldest plan first, FOR UPDATE SKIP LOCKED; a
  lease without a batch for 15 min passes to the next node and resumes at
  next_id), batch (stores files and fragments, moves next_id), finish,
  release, plan (from below live indexing / the backfill / earlier plans
  down to N days back; takes over the group's backfill), status.
- Seed API under /api/v1/seed (lease, ranges/:id/batches|done|release,
  status) behind a node-token middleware; JSON bodies up to 64 MB after
  gzip.
- seed:node runs a node: no database or Redis, outgoing HTTPS only, N
  connections, gzip batches, retries for network errors and 5xx, drops a
  range on 409, gives its ranges back on SIGTERM. seed-node/ has a compose
  file that builds the image from this repository.
- seed:token, seed:plan, seed:status for the operator. Header parsing moved
  to lib/ingest and the range loop to lib/seed/runner, shared by seed:range
  and seed:node.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

seed-node/node.env.example

@@ -0,0 +1,29 @@
+# --- Seed API: the orchestrator, and this node's token (`node ace seed:token <name>` on the indexer).
+SEED_URL=https://seed.exp.sforum.nl
+SEED_TOKEN=sn_replace_me
+# Ranges worked on at once; each uses one NNTP connection of the account below.
+SEED_CONNECTIONS=2
+
+# --- NNTP account this node fetches headers with (mind its connection limit across all nodes).
+NNTP_HOST=news.example.com
+NNTP_PORT=563
+NNTP_SECURE=true
+NNTP_USER=replace_me
+NNTP_PASSWORD=replace_me
+
+# --- Required by the app's configuration, but unused on a seeding node (no database, Redis or web server).
+NODE_ENV=production
+TZ=UTC
+PORT=3333
+HOST=0.0.0.0
+LOG_LEVEL=info
+APP_KEY=unused-on-seed-nodes-unused-on-seed-nodes
+APP_URL=http://localhost:3333
+SESSION_DRIVER=memory
+DB_CONNECTION=pg
+DB_HOST=localhost
+DB_PORT=5432
+DB_USER=unused
+DB_DATABASE=unused
+REDIS_HOST=localhost
+REDIS_PORT=6379