feat: live ticking one-time code in item detail

[pyramation]

Summary

Clicking an imported 2FA account in the vault list previously showed only its raw fields (a concealed seed, period, digits) — no actual code. ItemDetail now detects any item with a totp_seed-purpose field and renders a live one-time code panel above the fields: big monospace code (split for readability at any digit count), copy button with the 30s clipboard clear, and a countdown Progress bar, polling dcrypt.totp.code(item.id) every second (which already honours stored period/digits).

This works for any item kind that carries a TOTP seed, not just kind === 'totp' — e.g. logins with an attached seed.

Link to Devin session: https://app.devin.ai/sessions/04636534e07048089ffb6b78142e12cd
Requested by: @pyramation

[devin-ai-integration]

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