[FEATURE] Support Importing Account via 15-Word Full-Weight Seed Phrase in Extension

[Peppermint1020]

Description
Currently, the extension does not allow users to import accounts using a 15-word full-weight seed phrase. Many users rely on this type of seed phrase for account recovery and import across wallets. Adding support for this feature will enhance usability and compatibility with existing accounts.

Steps to Reproduce
(1)Open the extension and navigate to the account import section.
(2)Attempt to import an account using a 15-word full-weight seed phrase.
(3)Observe that the seed phrase is not accepted.

Expected Behavior
The extension should allow users to input a 15-word full-weight seed phrase to import their account successfully.

Actual Behavior
The extension currently does not support importing accounts using this type of seed phrase, leading to failed import attempts.

Environment
Platform: extension 2.5.22