docs(epi): clarify eligible transaction types for deferred tokenization

[alexdll31]

Summary

• Adds an Implementation notes item listing the five transaction types that support GET /transactions/{id}/token: sale, refund, preAuthorizationCapture, moToSale, moToRefund
• Explicitly states that other types return a 400 error
• Removes a now-redundant inline mention of the same list from the Backoffice tab only, so the constraint is visible regardless of which integration path the reader is on

Source: legacy portal wording + GET /transactions/{id}/token endpoint behaviour.

🤖 Generated with Claude Code

[AnnyTp]

thank you for making it explicit