**Improve database handling and disable redundant health checks**

- Added logic to construct `DATABASE_URL` from `DB_*` variables to prevent accidental fallback to SQLite during Docker Compose deployments.
- Updated `DATABASES` configuration to use `dj_database_url.parse` instead of deprecated `config`.
- Disabled health checks for services that do not expose a web port to avoid unnecessary probes.
- Removed unused `libmariadb-dev` and `pkg-config` dependencies from the `Dockerfile`.

Dockerfile

@@ -32,7 +32,7 @@ RUN . /etc/os-release \
     && echo "deb http://deb.debian.org/debian ${VERSION_CODENAME} non-free non-free-firmware" \
         > /etc/apt/sources.list.d/non-free.list \
     && apt update \
-    && apt install -y --no-install-recommends cron unrar libmariadb-dev pkg-config \
+    && apt install -y --no-install-recommends cron unrar \
     && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /src