Function optimize_max_age_for_startup 

pub fn optimize_max_age_for_startup(
    last_startup: Option<&str>,
    default_max_age: Option<u32>,
) -> Option<u32>

What: Calculate optimal max_age_days based on last startup timestamp.

Inputs:

• last_startup: Optional timestamp in YYYYMMDD:HHMMSS format.
• default_max_age: Default max age in days if no optimization applies.

Output:

• Optimized max_age_days value, or None to fetch all.

Details:

• If last startup was within 1 hour: use 1 day (recent data likely cached)
• If last startup was within 24 hours: use 2 days
• If last startup was within 7 days: use configured max_age or 7 days
• Otherwise: use configured max_age
• This reduces unnecessary fetching when the app was recently used.
• NOTE: This only affects Arch news and advisories date filtering. Package updates are ALWAYS fetched fresh to detect new packages and version changes.