fix: reject invalid conversation parameters

[evanmarshall]

Mirror of chatwoot#15623 for Ito QA evaluation.

Upstream PR: chatwoot#15623
Upstream author: @sojan-official
Upstream head commit: 2f14c65856c1bf0fbe8e894dbd1d2e471404ad54

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Conversation priority mutations and filters now reject malformed request values through Chatwoot's existing 422 Unprocessable Entity paths instead of allowing enum, bind, or database errors to reach Sentry.

Closes

• Sentry 6625387934
• Sentry 7288018570
• Sentry 7664169339

How to reproduce

• Send the unsupported priority: "none" value to a conversation priority endpoint. It previously reached the enum assignment and raised ArgumentError.
• Submit a conversation filter whose values contains an object. It previously reached Active Record as a structured bind value and raised TypeError.

What changed

• Route priority updates through the existing strong-parameter method and reject values outside the conversation priority enum.
• Remove the unsupported none value from the public priority API schemas.
• Reject structured filter values in the shared filter-condition validator while preserving scalar and scalar-array values.
• Document the request-boundary validation rule in AGENTS.md.