Phase 2 sub-commit 2: ModelPublisher + #[BridgeResource] + Doctrine listener

Bundle gains the model layer that bridges Doctrine entities to Mercure
without per-resource glue. Three new pieces:

- `#[BridgeResource(name: ?string)]` attribute marks an entity as a
  reactive bridge model. Topic name defaults to the lowercased class
  basename and can be overridden per resource.

- `ModelPublisher` translates entity changes into PLAN.md §4 envelopes
  ({op, id, data, version, ?correlationKey}) and dual-publishes them
  on `app://model/{name}` (collection topic) and `app://model/{name}/{id}`
  (entity topic). Entity normalisation goes through Symfony's Serializer
  (ObjectNormalizer + DateTime + BackedEnum) for predictable JSON. The
  envelope `version` field is a per-process monotonic counter — fine for
  single-instance dev mode; production should back this with a Postgres
  SEQUENCE or equivalent (noted for Phase 4).

- `DoctrineBridgeListener` registers `postPersist`/`postUpdate`/
  `postRemove` via `#[AsDoctrineListener]` and routes events through
  ModelPublisher. Entities without `#[BridgeResource]` are silently
  skipped.

Plus the correlation-key plumbing the §5 Update Semantics layer needs:

- `CorrelationContext` is a per-request holder for the originating
  request's `Idempotency-Key`.
- `CorrelationKeyListener` reads the header on `KernelEvents::REQUEST`
  and clears the context on `KernelEvents::TERMINATE` (worker mode
  hygiene). CLI mutations see no key, which is correct.

Bundle composer.json picks up `doctrine/dbal`, `doctrine/orm`,
`doctrine/doctrine-bundle`, `symfony/serializer`, `symfony/property-*`,
`symfony/uid`. PHPStan extension `phpstan-doctrine` added so the listener's
event-args types resolve. Skeleton's framework.yaml enables `serializer`
and `property_info`.

Tests: 5 new for ModelPublisher (dual publish, correlation echo, delete
op omits data, untagged entities ignored, version increments). Total:
16 tests, 45 assertions, PHPStan clean, cs-fixer clean.

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

framework/php/src/Attribute/BridgeResource.php

@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpQml\Bridge\Attribute;
+
+/**
+ * Marks a Doctrine entity as a reactive bridge resource.
+ *
+ * Tagged entities have their persist/update/remove events automatically
+ * mirrored onto the Mercure topics `app://model/{name}` and
+ * `app://model/{name}/{id}` (PLAN.md §4 *Push*, §6 *ModelPublisher*).
+ *
+ * The maker generated by Phase 2 sub-commit 4 produces entities with
+ * this attribute pre-attached.
+ */
+#[\Attribute(\Attribute::TARGET_CLASS)]
+final readonly class BridgeResource
+{
+    public function __construct(
+        /** Logical resource name used in topics. Defaults to lowercased class basename. */
+        public ?string $name = null,
+    ) {
+    }
+}