Add selective key migration for os keyring migration CLI

[metalarm10]

Description

Closes: https://app.clickup.com/t/868hh4h3a

Bulk migration is blocked on macOS: Keychain enforces per-item password prompts (2 dialogs per key), impractical for users with hundreds of keys.

This PR adds optional key name arguments to txd keys migrate-keyring, allowing users to migrate only the keys they need.

Usage:

txd keys migrate-keyring              # migrate all keys
txd keys migrate-keyring alice bob    # migrate only alice and bob

Reviewers checklist:

• Try to write more meaningful comments with clear actions to be taken.
• Nit-picking should be unblocking. Focus on core issues.

Authors checklist

• Provide a concise and meaningful description
• Review the code yourself first, before making the PR.
• Annotate your PR in places that require explanation.
• Think and try to split the PR to smaller PR if it is big.

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This change is 

[miladz68]

@miladz68 reviewed 1 file and all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on masihyeganeh, TxCorpi0x, and ysv).

[ysv]

@ysv reviewed 1 file and all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on masihyeganeh and TxCorpi0x).