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/phpunit.xml.dist

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
+         bootstrap="vendor/autoload.php"
+         colors="true"
+         cacheDirectory=".phpunit.cache"
+         executionOrder="random"
+         failOnRisky="true"
+         failOnWarning="true">
+    <testsuites>
+        <testsuite name="bridge">
+            <directory>tests/</directory>
+        </testsuite>
+    </testsuites>
+
+    <source>
+        <include>
+            <directory>src</directory>
+        </include>
+    </source>
+</phpunit>