Support --label in Custom Docker Options for standalone databases

[dionysm]

Right now, standalone databases can't get custom labels.
I switched to standalone databases because backups and imports are much easier there.
We run a lot of containers and DBs, and tools like Dozzle get messy fast without proper grouping (dev.dozzle.group) or readable aliases (dev.dozzle.name).

DBs only have the "Custom Docker Options" field, but --label gets silently dropped there.
Applications have "Container Labels", databases have nothing.

Proposal

• Support --label in "Custom Docker Options" (multiple allowed), e.g. --label dev.dozzle.group=shop-stage --label dev.dozzle.name=shop-stage-db
• For databases, add these labels on top of Coolify's own labels
• Ignore labels starting with coolify., so status tracking and backups won't break
• Applications ignore --label (with a note in the deployment log), since they already have "Container Labels"

It's a small change (3 files plus tests). I already have it working and tested on a local dev instance:
https://github.com/dionysm/coolify/tree/feat/database-custom-labels

Would you accept a PR for this against next? Happy to adjust the approach.