feat(13-01): add the prohibited rule and dated-download and notification masks

- lagoon.ValidateRequest supports Laravel 9 prohibited (!required, not
  implicit); with no catalog line its message is validation.prohibited
- tide compares Content-Disposition with real calendar dates masked on both
  sides; a different name, an invalid date or a one-sided date still diffs
- tide.NormalizePublications masks a Carbon +00:00 $.data.payload.created_at
  and an uncaptured positive integer $.data.payload.id as {{id}}
- the album-date test's outside-album sibling moves off payload.created_at,
  which now has its own mask
- READMEs and docs describe the rule and both masks

docs/database/casts-and-validation.md

@@ -127,6 +127,7 @@ The behaviour follows Laravel:
 - The other rules run only when there is a value: they skip an absent attribute, a blank string, `null` under `nullable` and an absent key under `sometimes`.
 - `min`, `max`, `size` and `between` measure what Laravel measures: the number on an `integer` or `numeric` attribute, compared exactly as a decimal; the number of elements of an array; the size of an uploaded file in kilobytes; otherwise the length in characters, not bytes. Each picks the matching message, such as `max.string` or `max.file`.
 - `email` is PHP's `FILTER_VALIDATE_EMAIL`, the check WinterCMS uses by default, so `user@localhost` is refused. `date` accepts ISO 8601 dates and date-times, `Y/m/d`, `m/d/Y`, `d.m.Y` and `d-m-Y`, and refuses dates that do not exist. `after_or_equal` and `before_or_equal` take a date, `today`, `tomorrow`, `yesterday` or `now` (in UTC), or the name of another field.
+- `prohibited` refuses a field the endpoint must never accept: it fails for any value that `required` would accept, including `0`, `false` and a non-empty array. Like the other non-implicit rules it never runs for an absent key or a blank string, and `null` or an empty array passes. Laravel 9's catalogs have no line for it, so the message is the key itself, `validation.prohibited`, as the PHP endpoint answers.
 - `exists:table,column` counts matching rows in the database, so it needs the transaction handle. Like Laravel it does not skip soft-deleted rows, and it does not run once the attribute already has a message.
 - File rules (`file`, `image`, `mimes` and the size rules) take a `lagoon.UploadedFile`; `lagoon.UploadedFileFromHeader` builds one from a parsed multipart part. The type is read from the file content, not from its name.