Add tenant dashboard (Phase 2)

Dashboard Features:
- Login page with session-based auth
- Overview page with live stats (viewers, stream status)
- Stream settings (URL, type configuration)
- Branding editor (colors, texts, custom CSS)
- Settings page (weather, content toggles, UI options)

New Files:
- dashboard/index.php: Main overview with stats
- dashboard/login.php: Authentication page
- dashboard/logout.php: Session cleanup
- dashboard/stream.php: Stream configuration
- dashboard/branding.php: Visual customization
- dashboard/settings.php: Feature toggles
- dashboard/templates/layout.php: Shared layout
- dashboard/api/stats.php: Stats API endpoint
- dashboard/assets/dashboard.css: Modern dashboard UI
- dashboard/assets/dashboard.js: Client-side functionality
- src/Auth/AuthManager.php: Secure auth with Argon2, remember-me

Auth Features:
- Secure password hashing (Argon2ID)
- Remember-me tokens
- Role-based access (super_admin, tenant_admin, tenant_user)
- Legacy fallback for existing admin credentials

aurora-livecam/dashboard/logout.php

@@ -0,0 +1,18 @@
+<?php
+/**
+ * Dashboard Logout
+ */
+
+require_once dirname(__DIR__) . '/vendor/autoload.php';
+
+if (file_exists(dirname(__DIR__) . '/src/bootstrap.php')) {
+    require_once dirname(__DIR__) . '/src/bootstrap.php';
+}
+
+use AuroraLivecam\Auth\AuthManager;
+
+$auth = new AuthManager();
+$auth->logout();
+
+header('Location: /dashboard/login.php');
+exit;