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

compose.yaml

@@ -9,7 +9,6 @@ services:
     environment:
       APP_ENV: prod
       APP_DEBUG: '0'
-      DATABASE_URL: sqlite:////data/essens.db
       DEFAULT_URI: https://essen.ljh31.de
       KEYCLOAK_ISSUER: https://iam.ljh31.de/realms/family
       KEYCLOAK_CLIENT_ID: essen