feat: Integrate join URL and QR code for player access

Adds a dynamic join URL and QR code displayed on the spectator view and host dashboard. This allows players to easily join the quiz session by scanning the QR code or navigating to the provided URL.

The `joinUrl` is now managed within the `GameContext` and exposed to relevant components. The spectator view uses this URL to generate the QR code, while the host view displays it for easy access. This enhances the onboarding experience for new players and simplifies session management.

database.sql

@@ -0,0 +1,18 @@
+
+CREATE TABLE IF NOT EXISTS `game_state` (
+  `id` int(11) NOT NULL AUTO_INCREMENT,
+  `game_data` longtext NOT NULL,
+  `updated_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+  PRIMARY KEY (`id`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
+
+CREATE TABLE IF NOT EXISTS `player_intents` (
+  `id` int(11) NOT NULL AUTO_INCREMENT,
+  `type` varchar(50) NOT NULL,
+  `payload` longtext NOT NULL,
+  `created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  PRIMARY KEY (`id`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
+
+-- Initialize with one row
+INSERT INTO `game_state` (`id`, `game_data`) VALUES (1, '{}') ON DUPLICATE KEY UPDATE `id`=1;