AO3-7260 Increase required password length

[not-varram]

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• Have you added tests for any changed functionality?
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Issue

https://otwarchive.atlassian.net/browse/AO3-7260

Purpose

Increases password length requirements to improve account security:

• User passwords: 8-72 characters (previously 6-40)
• Admin passwords: 10-72 characters (previously 10-40)
• Updates validation message to say "characters" instead of "letters"

The new 72-character maximum aligns with bcrypt's upper limit.

Testing Instructions

Full testing instructions are available in the Jira issue linked above.

Credit

varram (he/him)

[not-varram]

Oh- Forgot to update some other tests for the updated 8 char password min in 2 tests; I'm gonna quickly do that :)

[brianjaustin]

Thanks!