fix: accept a plain number of seconds as a duration

[davlgd]

Closes #1163

Context

A plain number of seconds passed to --after or --before becomes an invalid date: clever logs shows no logs without any error.

Proposal

• parseSimpleDuration() throws when there is no known unit, so the fallback on a number of seconds is reached
• This fallback only accepts digits, so 10x is rejected instead of read as 10 seconds

How to test

clever logs --after 3600 --before 1s   # before: no logs, after: logs of the last hour
clever logs --after 10x                # before: no logs, after: "Invalid duration" error
clever logs --after 1h --before 1s     # unchanged

[github-actions]

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[pdesoyres-cc]

LGTM

[hsablonniere]

Looked into whether this could be expressed more declaratively with Zod (a union of duration/date schemas). It's feasible, but the rest of the codebase isn't there yet (still JS, not TypeScript). Once we're fully on TypeScript, moving this kind of parsing/validation logic to Zod schemas will be worth revisiting.

Approving as is.