Migriere Persistenz von SQLite zu PostgreSQL (postgresql.lan:5432/essens)

- Dockerfile: pdo_pgsql installieren
- migrations: Postgres-Dialekt (SERIAL, TIMESTAMP(0), TEXT)
- compose/.env(.dist): postgresql://DATABASE_URL (Passwort via .env.local)
- bin/migrate-sqlite-to-pg.sh: einmaliger Datenimport SQLite->PG

composer.json

@@ -7,6 +7,7 @@
         "php": ">=8.2",
         "ext-ctype": "*",
         "ext-iconv": "*",
+        "ext-pgsql": "*",
         "doctrine/doctrine-bundle": "^3.3",
         "doctrine/doctrine-migrations-bundle": "^4.0",
         "doctrine/orm": "^3.7",