Phase 2 sub-commit 1: Doctrine ORM 3 + Migrations + SQLite

Skeleton gains Doctrine ORM 3.6 (with DoctrineBundle 3.x and Migrations
4.x), pointed at a SQLite file under var/data.sqlite. Apps move to
Postgres/MySQL by overriding DATABASE_URL in .env.local.

config/packages/doctrine.yaml registers the symfony/uid UuidType so
Phase 2 sub-commit 4's UUIDv7 default works without per-app config,
and pre-wires the App\Entity attribute mapping under src/Entity/ for
the maker to drop entities into.

Bundle gains an optional doctrine/dbal Connection via Autowire; when
present, bridge:doctor adds a "Database reachable" SELECT-1 probe.
The bundle still installs cleanly without doctrine/dbal — apps that
opt out get a doctor table without the database row.

Verified: `bin/console bridge:doctor` is all green against a fresh
SQLite. composer quality (PHPStan + cs-fixer + PHPUnit) stays green.

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

framework/skeleton/symfony/config/bundles.php

@@ -4,5 +4,7 @@ return [
     Symfony\Bundle\FrameworkBundle\FrameworkBundle::class => ['all' => true],
     Symfony\Bundle\SecurityBundle\SecurityBundle::class => ['all' => true],
     Symfony\Bundle\MercureBundle\MercureBundle::class => ['all' => true],
+    Doctrine\Bundle\DoctrineBundle\DoctrineBundle::class => ['all' => true],
+    Doctrine\Bundle\MigrationsBundle\DoctrineMigrationsBundle::class => ['all' => true],
     PhpQml\Bridge\BridgeBundle::class => ['all' => true],
 ];