feat(torrent): library.js SQLite + purge selection (ref #917)

Adds SQLite-backed torrent library (add/list/get/touch/keep/remove) and
the expiredEphemeral() query the purge job uses to find stale
kept=0 torrents (last_played_at < now-ttl). Includes package-lock.json
and a lxc/app .gitignore for node_modules.

Co-Authored-By: Gerald KERMA <devel@cybermind.fr>

packages/secubox-torrent/lxc/app/.gitignore

@@ -0,0 +1 @@
+node_modules/

packages/secubox-torrent/lxc/app/library.js

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+// SPDX-License-Identifier: LicenseRef-CMSD-1.0
+// Copyright (c) 2026 CyberMind — Gérald Kerma <devel@cybermind.fr>
+// SecuBox-Deb :: secubox-torrent :: library.js — CyberMind https://cybermind.fr
+//
+// SQLite-backed torrent library: ephemeral (kept=0) vs. kept torrents, plus
+// the selection query used by the purge job to find stale ephemeral entries.
+
+import Database from 'better-sqlite3';
+
+export class Library {
+  constructor(dbPath) {
+    this.db = new Database(dbPath);
+    this.db.exec(`CREATE TABLE IF NOT EXISTS torrents (
+      infohash TEXT PRIMARY KEY, name TEXT, magnet TEXT, path TEXT,
+      added_at INTEGER, last_played_at INTEGER, kept INTEGER DEFAULT 0)`);
+  }
+  add({ infohash, name, magnet, path }) {
+    const now = Math.floor(Date.now() / 1000);
+    this.db.prepare(`INSERT OR REPLACE INTO torrents
+      (infohash,name,magnet,path,added_at,last_played_at,kept)
+      VALUES (?,?,?,?,?,?,0)`).run(infohash, name, magnet, path, now, now);
+  }
+  list() { return this.db.prepare('SELECT * FROM torrents ORDER BY added_at DESC').all(); }
+  get(infohash) { return this.db.prepare('SELECT * FROM torrents WHERE infohash=?').get(infohash) || null; }
+  touch(infohash) { this.touchAt(infohash, Math.floor(Date.now() / 1000)); }
+  touchAt(infohash, ts) { this.db.prepare('UPDATE torrents SET last_played_at=? WHERE infohash=?').run(ts, infohash); }
+  keep(infohash, newPath) { this.db.prepare('UPDATE torrents SET kept=1, path=? WHERE infohash=?').run(newPath, infohash); }
+  remove(infohash) { this.db.prepare('DELETE FROM torrents WHERE infohash=?').run(infohash); }
+  expiredEphemeral(ttlSeconds, now = Math.floor(Date.now() / 1000)) {
+    const cutoff = now - ttlSeconds;
+    return this.db.prepare('SELECT infohash FROM torrents WHERE kept=0 AND last_played_at < ?')
+      .all(cutoff).map(r => r.infohash);
+  }
+}

packages/secubox-torrent/lxc/app/library.test.js

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+// SPDX-License-Identifier: LicenseRef-CMSD-1.0
+// Copyright (c) 2026 CyberMind — Gérald Kerma <devel@cybermind.fr>
+// SecuBox-Deb :: secubox-torrent :: library.test.js — CyberMind https://cybermind.fr
+//
+// Tests for the SQLite-backed torrent library + ephemeral purge selection.
+
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { Library } from './library.js';
+
+const mk = () => new Library(':memory:');
+
+test('add then list yields one ephemeral row', () => {
+  const lib = mk();
+  lib.add({ infohash: 'a', name: 'A', magnet: 'm', path: '/tmp/a' });
+  const rows = lib.list();
+  assert.equal(rows.length, 1);
+  assert.equal(rows[0].kept, 0);
+});
+
+test('keep flips kept and updates path', () => {
+  const lib = mk();
+  lib.add({ infohash: 'a', name: 'A', magnet: 'm', path: '/tmp/a' });
+  lib.keep('a', '/data/torrent/library/a');
+  assert.equal(lib.get('a').kept, 1);
+  assert.equal(lib.get('a').path, '/data/torrent/library/a');
+});
+
+test('expiredEphemeral returns only stale unkept torrents', () => {
+  const lib = mk();
+  lib.add({ infohash: 'old', name: 'O', magnet: 'm', path: '/tmp/o' });
+  lib.add({ infohash: 'fresh', name: 'F', magnet: 'm', path: '/tmp/f' });
+  lib.add({ infohash: 'kept', name: 'K', magnet: 'm', path: '/tmp/k' });
+  lib.touchAt('old', 1000); lib.touchAt('fresh', 9000); lib.touchAt('kept', 1000);
+  lib.keep('kept', '/data/k');
+  const exp = lib.expiredEphemeral(3600, 10000); // now=10000, ttl=3600 → cutoff 6400
+  assert.deepEqual(exp, ['old']);
+});