The application crashes with a JSON unmarshaling error when processing
data from a paid member session. This is caused by the `delivery_date`
field, which is expected to be a "MM/DD" string, sometimes being sent
as a number (e.g., 23744) for older episodes accessible to paid members.

This commit fixes the crash and correctly handles both data types by
implementing a prioritized date-finding strategy, preserving the
original logic's structure.

1.  The `delivery_date` field in the `nuxt.Content` struct is changed to
    `interface{}` to accept both strings and numbers, preventing the
    initial crash.

2.  The `Episodes()` method is augmented to be type-aware, following a
    strict priority for determining an episode's date:
    - **Priority 1**: If `delivery_date` is a string, the original,
      preferred `GuessTime` logic is used.
    - **Last Resort**: If `delivery_date` is a number, a new helper
      function, `dateFromURL`, is called to parse the full date from
      the episode's `streaming_url` filename. This is only used when
      the string date is not present.

3.  The initial "anchor-finding" loop is also made type-safe to avoid
    errors when processing episodes with numeric dates.

This resolves the bug for paid sessions by correctly parsing dates from
the streaming URL as a fallback, while ensuring the original guessing
logic is preserved for all other cases, preventing regressions.