feat: ticker symbol voting for live votes

- Add ticker column to games table with migration
- Bootstrap tickers from tickers.json config on startup
- POST /api/votes/live accepts optional ticker field for direct game
  lookup (bypasses timestamp-interval matching)
- Ticker votes work for any game, not just session games
- Update API docs and add e2e tests for ticker voting
- Version bump to 0.6.5

Made-with: Cursor

backend/database.js

@@ -125,6 +125,19 @@ function initializeDatabase() {
     // Column already exists, ignore error
   }
 
+  // Add ticker column for ticker-symbol voting
+  try {
+    db.exec(`ALTER TABLE games ADD COLUMN ticker TEXT`);
+  } catch (err) {
+    // Column already exists, ignore error
+  }
+
+  try {
+    db.exec(`CREATE UNIQUE INDEX IF NOT EXISTS idx_games_ticker ON games(ticker)`);
+  } catch (err) {
+    // Index already exists, ignore error
+  }
+
   // Migrate existing popularity_score to upvotes/downvotes if needed
   try {
     const gamesWithScore = db.prepare(`