album-tools v0.1.21

Enhanced date tag auditing (v0.1.21)

 * Improved the `audit_date_tags()` function to accept and correctly validate date tags in any of the following formats:
     * `YYYY` (e.g., `1987`) — must be an integer year between 1900 and 2100.
     * `YYYY-MM` (e.g., `1987-05`) — must be a valid year (1900–2100) and a valid month (01–12).
     * `YYYY-MM-DD` (e.g., `1987-05-07`) — must be a valid date and year within the allowed range.

 * Malformed, out-of-range, and non-conforming date tags are now properly logged as issues in the audit output.