Seed plans fill every uncovered gap, with priorities; cheaper ingest and file storing

- seed:plan plans every part of a group's history no range covers (it
  started below the lowest known range and left a.b.ath's 13 most recent
  months out); seed_ranges.priority orders leases (seed:plan --priority).
- binaries.part_count, kept by the parts insert in the same statement:
  claimCompleted compares it instead of counting parts every batch.
- file_keys: 64-bit hashes of all file keys; FileStore.insert asks it
  before probing every files partition.
- worker:file stores 100 completed binaries per job with set-based queries.

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

database/migrations/1768620765200_seed_range_priority.ts

@@ -0,0 +1,14 @@
+import { BaseSchema } from '@adonisjs/lucid/schema'
+
+/** Seed ranges of a higher priority are leased first (`seed:plan --priority`), e.g. a gap in recent history. */
+export default class extends BaseSchema {
+  async up() {
+    this.schema.alterTable('seed_ranges', (table) => {
+      table.smallint('priority').notNullable().defaultTo(0)
+    })
+  }
+
+  async down() {
+    this.schema.alterTable('seed_ranges', (table) => table.dropColumn('priority'))
+  }
+}