Cherry-pick: Allow colon in DSN database name (#1568)

## Upstream PR
https://github.com/dimitri/pgloader/pull/1568

## Summary
Adds `#\:` (colon) to allowed characters in database name parsing, supporting Xata's `db:branch` naming pattern.

## Files
- `src/parsers/command-db-uri.lisp`

## Notes
- Low risk, 1-line addition
- Niche use case (Xata)
- **Priority: Lower**