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/composer.json

@@ -10,6 +10,10 @@
         "symfony/yaml": "^8.0",
         "symfony/security-bundle": "^8.0",
         "symfony/mercure-bundle": "^0.4",
+        "symfony/uid": "^8.0",
+        "doctrine/orm": "^3.0",
+        "doctrine/doctrine-bundle": "^3.0",
+        "doctrine/doctrine-migrations-bundle": "^4.0",
         "php-qml/bridge": "@dev"
     },
     "autoload": {