Time ago timestamps: Use days instead of months when we're under 90 days

[noahtalerman]

Goal

User story
As a Fleet user looking at time ago timestamps,
I want to see "days" instead of "months" when the timestamp is less than 90 days ago
so that I can see a more helpful timestamp.

For help creating a user story, see "Writing a good user story" in the website handbook.

Change

• Time ago timestamps: use days instead of months when under 90 days #48964

Engineering

• Test plan is finalized

Test plan

• A timestamp 30–89 days old shows as "X days ago" (e.g. host last seen, activity feed, dashboard, EULA/bootstrap package/profile "Uploaded", certificates "Updated").
• A timestamp ≥90 days old still shows in months (e.g. "3 months ago").
• A timestamp <30 days old is unaffected (still shows days/hours/minutes as before).

Edge cases

• TODO
• TODO
• TODO

Supplemental testing

Testing notes

Confirmation

1. Engineer: Added comment to user story confirming successful completion of test plan (include any special setup, test data, or configuration used during development/testing if applicable).
2. QA: Added comment to user story confirming successful completion of test plan.
3. QA: Determined whether this story needs Playwright automation.
   • Needs automation: Yes / No
   • If yes, filed a follow-up issue in the :help-qa project with status "Needs automation": TODO