Add PostgreSQL automatic database initialization support

[meyeringh]

Hey man, love your work on this. I have been using your container in my cluster, but im trying to move away from mysql and only use postgres in there. For k8s i need the automatic db init feature. So here is the PR for it :D.

Summary

• Extends automatic database initialization to support PostgreSQL (in addition to MySQL/MariaDB)
• Database type is now configurable via DB_TYPE environment variable (mysql, postgres)
• Added PostgreSQL client and schema file for automated setup (I just dumped this from an up to date instance of webtrees + postgres. )

Basically: the change is backwards compatible: If you dont do anything different you use mysql, if you specify postgres as DB_TYPE you get the db init for postgres. Let me know if you want me to change anything on this.

btw, this is the docker-compose I used to test this. Not sure if you want this in your repo so im leaving this here:

services:
  postgres:
    image: postgres:18
    container_name: webtrees-postgres
    environment:
      POSTGRES_DB: webtrees
      POSTGRES_USER: webtrees
      POSTGRES_PASSWORD: webtrees1234
    ports:
      - "5432:5432"
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U webtrees"]
      interval: 5s
      timeout: 5s
      retries: 5

  webtrees:
    build:
      context: .
      dockerfile: Dockerfile
    container_name: webtrees-app
    ports:
      - "8080:80"
    environment:
      - DB_HOST=postgres
      - DB_USER=webtrees
      - DB_PASSWORD=webtrees1234
      - DB_NAME=webtrees
      - DB_TYPE=postgres
      - WT_ADMIN=admin
      - WT_ADMINPW=admin12345
      - WT_ADMINMAIL=admin@webtrees.local
      - DISABLE_SSL=TRUE
      - PORT=80
    depends_on:
      postgres:
        condition: service_healthy

[H2CK]

Thank you for this PR. Could you additionally add a folder docker-compose were you add your docker-compose example.

Btw. the pipeline for this PR currently fails due to some problems in the Github Actions. I will take care for this later, but it should not affect your changes.

[meyeringh]

Alright, i added the docker compose to a folder 👍

[H2CK]

I will release a new version, which contains these changes in the next days.