feat: precompute stream grouping during source sync (#13)

Move variant grouping work out of Live TV rendering into the
catalog pipeline: a liveProjectionService builds the logical channel
projection (schema in liveProjectionSchema) whenever a source is
added, synced or modified (name change, new address), and the
projection is served through a /live route. ChannelList now consumes
the precomputed projection via a liveChannelProjection client
service, recalculating only when the catalog changes. Cover
projection building, incremental recompute and client consumption
with tests.

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

server/db/liveProjectionSchema.js

@@ -0,0 +1,49 @@
+const LIVE_PROJECTION_COLUMNS = {
+    logical_channel_id: 'TEXT',
+    grouping_fingerprint: 'TEXT',
+    grouping_input_hash: 'TEXT',
+    quality_label: 'TEXT',
+    quality_rank: 'INTEGER',
+    variant_rank: 'INTEGER',
+    language_code: 'TEXT',
+    language_confidence: 'REAL',
+    language_scores: 'JSON',
+    language_evidence: 'JSON',
+    language_detector: 'TEXT',
+    language_input_hash: 'TEXT'
+};
+
+const LIVE_PROJECTION_SCHEMA_SQL = `
+    CREATE INDEX IF NOT EXISTS idx_items_logical_channel ON playlist_items(logical_channel_id);
+    CREATE INDEX IF NOT EXISTS idx_items_grouping_fingerprint ON playlist_items(grouping_fingerprint);
+
+    CREATE TABLE IF NOT EXISTS logical_channels (
+        id TEXT PRIMARY KEY,
+        fingerprint TEXT NOT NULL UNIQUE,
+        display_name TEXT NOT NULL,
+        preferred_variant_id TEXT,
+        variant_count INTEGER NOT NULL DEFAULT 0,
+        created_at INTEGER NOT NULL,
+        updated_at INTEGER NOT NULL
+    );
+    CREATE INDEX IF NOT EXISTS idx_logical_channels_fingerprint ON logical_channels(fingerprint);
+
+    CREATE TABLE IF NOT EXISTS catalog_projection_state (
+        projection TEXT PRIMARY KEY,
+        status TEXT NOT NULL,
+        started_at INTEGER,
+        completed_at INTEGER,
+        input_hash TEXT,
+        projected_count INTEGER NOT NULL DEFAULT 0,
+        error TEXT
+    );
+`;
+
+function ensureColumns(database, table, columns) {
+    const existing = new Set(database.prepare(`PRAGMA table_info(${table})`).all().map(column => column.name));
+    for (const [name, definition] of Object.entries(columns)) {
+        if (!existing.has(name)) database.exec(`ALTER TABLE ${table} ADD COLUMN ${name} ${definition}`);
+    }
+}
+
+module.exports = { ensureColumns, LIVE_PROJECTION_COLUMNS, LIVE_PROJECTION_SCHEMA_SQL };

server/db/sqlite.js

@@ -1,6 +1,11 @@
 const Database = require('better-sqlite3');
 const path = require('path');
 const fs = require('fs');
+const {
+    ensureColumns,
+    LIVE_PROJECTION_COLUMNS,
+    LIVE_PROJECTION_SCHEMA_SQL
+} = require('./liveProjectionSchema');
 
 const dataDir = path.join(__dirname, '..', '..', 'data');
 const dbPath = path.join(dataDir, 'content.db');
@@ -73,6 +78,9 @@ function initSchema() {
         CREATE INDEX IF NOT EXISTS idx_items_category ON playlist_items(source_id, category_id);
     `);
 
+    ensureColumns(db, 'playlist_items', LIVE_PROJECTION_COLUMNS);
+    db.exec(LIVE_PROJECTION_SCHEMA_SQL);
+
     // EPG Programs
     // Optimized for range queries
     db.exec(`
@@ -247,6 +255,8 @@ const layaLanguageCache = {
 module.exports = {
     getDb,
     initSchema,
+    ensureColumns,
+    LIVE_PROJECTION_COLUMNS,
     favorites,
     layaLanguageCache
 };