deploy.sh: add --quiet flag to reduce terminal output

[lgelauff]

Background

tools/deploy.sh is intentionally verbose for interactive use. As the script matures and deploys become routine, it would be useful to suppress the step-by-step output.

Proposed behaviour

• --quiet (or -q) suppresses per-step progress lines, printing only warnings, errors, and the final result line
• All suppressed output is still written to a log file (e.g. ~/deploy-<timestamp>.log) so it can be reviewed if something goes wrong
• Alternatively, a simple --quiet that just redirects verbose output to /dev/null with no log

Acceptance criteria

• bash deploy.sh --ref master behaves exactly as today (no regression)
• bash deploy.sh --ref master --quiet prints only the final "Deploy complete" line (plus any warnings/errors)