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/channelLanguageFusion.test.js

@@ -0,0 +1,41 @@
+const test = require('node:test');
+const assert = require('node:assert/strict');
+const fusion = require('../public/js/services/channelLanguageFusion.js');
+
+const algo = {
+    language: { code: 'fr', label: 'French', confidence: 70, status: 'medium' },
+    languageScores: { fr: 70, en: 30 },
+    languageEvidence: [{ code: 'fr', weight: 60, type: 'name-prefix', value: 'FR' }]
+};
+
+test('Laya-only mode maps backend confidence and language', () => {
+    const result = fusion.applyLanguageMode(algo, { language: 'en', confidence: 0.88 }, 'laya');
+    assert.deepEqual(result.language, { code: 'en', label: 'English', confidence: 88, status: 'high' });
+    assert.equal(result.languageEvidence[0].type, 'laya');
+});
+
+test('hybrid mode combines Laya and algorithm evidence', () => {
+    const result = fusion.applyLanguageMode(algo, { language: 'en', confidence: 0.9 }, 'hybrid');
+    assert.equal(result.language.code, 'en');
+    assert.ok(result.languageScores.en > result.languageScores.fr);
+    assert.deepEqual(result.languageEvidence.map(item => item.type), ['name-prefix', 'laya']);
+});
+
+test('hybrid mode safely preserves algorithm output without Laya', () => {
+    assert.equal(fusion.applyLanguageMode(algo, null, 'hybrid'), algo);
+});
+
+test('batch descriptors contain only safe metadata in the backend id/text contract', () => {
+    const descriptor = fusion.buildLayaDescriptor({
+        sourceId: 4,
+        name: '|FR| Sports',
+        groupTitle: 'Sports',
+        sourceName: 'Provider',
+        tvgId: 'sports.fr',
+        url: 'https://user:secret@example.test/live'
+    }, '4:channel-1', algo);
+    assert.deepEqual(Object.keys(descriptor), ['id', 'text']);
+    assert.equal(descriptor.id, '4:channel-1');
+    assert.match(descriptor.text, /sourceId: 4/);
+    assert.doesNotMatch(descriptor.text, /secret|https:\/\//);
+});