feat: show rate-limit reset expiry

[ClaudiuSchuster]

Summary

• show the next available earned rate-limit reset expiry as local date and time
• add a compact remaining countdown and urgency styling: orange inside seven days, neon-pink breathing inside 24 hours
• keep the zero-reset state as Rate-limit resets: 0 without extra suffix content
• refresh the four README popup screenshots with the final two-line credit display

Validation

• make verify
• Super-Linter 8.7.0
• live Cinnamon deployment audit: EXPECTED=10 VALID=10 SYMLINKS=0 MISMATCHES=0
• visual QA of all four refreshed README screenshots on Cinnamon 6.6.9