feat: add optional Laya engine mode for grouping and language detection (#12)

Add a languageDetectionMode setting (algo | laya | laya+algo) exposed
in Settings with three engine choices. When Laya is enabled, a laya
service (Dockerfile.laya, optional compose profile, models stored
outside the repo under ./data/models/laya) can be started, with model
download and deletion from the UI via /laya routes to manage disk
space. Add a channelLanguageFusion service combining Laya results
with the existing algorithm, and wire detection mode through
grouping, channel list and player. Cover engine selection, fusion
and laya service behavior with tests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

test/settingsDefaults.test.js

@@ -5,3 +5,7 @@ const { getDefaultSettings } = require('../server/db');
 test('defaults Live TV channel lists to grouped mode', () => {
     assert.equal(getDefaultSettings().liveChannelListMode, 'grouped');
 });
+
+test('defaults language detection to the safe algorithmic mode', () => {
+    assert.equal(getDefaultSettings().languageDetectionMode, 'algo');
+});