feat(multisig): import a shared account by scanning its QR code

[yasin-ce]

Description

Adds an Import Shared Account flow. Scanning a multisig QR resolves the multisig metadata from the backend, shows version / threshold / participant addresses on a preview screen, and routes into the existing NameMultisigScreen with importParams so the account can be persisted without re-deriving its address. Wires the new screen into the multisig routes and the deeplink parser, and adds i18n copy.

Related Issues

• closes https://algorandfoundation.atlassian.net/browse/PERA-#

Checklist

• Have you tested your changes locally?
• Have you reviewed the code for any potential issues?
• Have you documented any necessary changes in the project's documentation?
• Have you added any necessary tests for your changes?
• Have you updated any relevant dependencies?

Additional Notes

Crypto-feature checklist (per team convention):

• Typed errors — UI hooks surface errors via the existing toast pattern; no new error classes needed for this flow (no key material touched).
• Preserves every source field — import payload carries version, threshold, addresses, and address; all four are threaded through NameMultisigScreen and persisted.
• Swallowed errors — none added.
• Verifies, doesn't trust — see the open item below; the imported address is currently trusted verbatim rather than derived from (version, threshold, addresses) and asserted equal.
• Scope — surface is just the new screen + routes + parser branch; no speculative exports.

Open follow-ups before merge (raised in code review):

• useNameMultisigScreen.ts (~line 105) takes importParams.address verbatim. Recommend deriving via generateMultisigAddress(version, threshold, addresses) and asserting equality before calling createMultisigMutation so a backend / payload inconsistency can't persist an account whose address disagrees with its own participant list.