Phase 1 sub-commit 2: Symfony bundle internals

Bundle code for php-qml/bridge: BridgeBundle (AbstractBundle, autoloads
config/services.yaml), Publisher (thin wrapper over Mercure HubInterface
that enforces envelope-as-JSON), SessionAuthenticator (bearer-token
custom Symfony authenticator with problem+json failures), and
HealthController (GET /healthz readiness probe).

Composer constraints bumped to Symfony ^8.0 across the board (per user
request); mercure component to ^0.7. PHPUnit 11 suite covers Publisher
publish + private flag and SessionAuthenticator support/auth/failure
paths — 8 tests, 22 assertions, all green.

PLAN.md §13 updated to record the Symfony 8 minimum.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

framework/php/src/BridgeBundle.php

@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpQml\Bridge;
+
+use Symfony\Component\Config\Definition\Configurator\DefinitionConfigurator;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;
+use Symfony\Component\HttpKernel\Bundle\AbstractBundle;
+
+final class BridgeBundle extends AbstractBundle
+{
+    public function loadExtension(array $config, ContainerConfigurator $container, ContainerBuilder $builder): void
+    {
+        $container->import(__DIR__ . '/../config/services.yaml');
+    }
+
+    public function configure(DefinitionConfigurator $definition): void
+    {
+        // Bundle config tree gains nodes when bridge:doctor and the
+        // skeleton's wiring need settable knobs (Phase 1 sub-commits 3 & 6).
+    }
+}