feat: add Batch PSBT signing UI demo

[Shoyo1024]

Summary

• Add a Batch PSBT Signing demo entry to Developer Settings and UI Gallery.
• Show a unified overview with transaction count, total outgoing amount, total network fee, and 15 mock PSBT transactions.
• Reuse the existing TxConfirm screen when opening a single transaction from the batch.
• Provide separate software-wallet and hardware-wallet previews: one authorization for software wallets, and sequential confirmation progress for hardware wallets.

Scope

• UI/demo implementation with mock transactions and account-matched mock PSBTs.
• No production DApp signPsbts request integration yet.
• No firmware batch-signing protocol changes.
• Signing detail uses signOnly; this flow does not broadcast transactions.
• Hardware progress is currently simulated for UI review and must be driven by real device callbacks in production.

Validation

• Targeted oxlint passed for all 8 changed files.
• Pre-commit lint:staged passed with 0 warnings and 0 errors.
• Pre-commit TypeScript check passed.
• git diff --check passed.

Related

• OK-59953