fix(server): valid backups with DB_URL env variable config

[peterbuga]

Description

Fixes generation of valid backups when using DB_URL config variable that need a password too passed to pg_dumpall utility, otherwise the Immich backup process will hang and generate 0-sized archives.

Fixes #21550

How Has This Been Tested?

Tests have been done as proposed in the issue discussion.

Checklist:

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation if applicable
• I have no unrelated changes in the PR.
• I have confirmed that any new dependencies are strictly necessary.
• I have written tests for new code (if applicable)
• I have followed naming conventions/patterns in the surrounding code
• All code in src/services/ uses repositories implementations for database calls, filesystem operations, etc.
• All code in src/repositories/ is pretty basic/simple and does not have any immich specific logic (that belongs in src/services/)

Please describe to which degree, if any, an LLM was used in creating this pull request.

No LLM used.