Signers UI test d68f81f

Test prerelease for Signers UI polish.

Commit: d68f81f

Changes:

• Signers now opens as a saved-signer list with a + button to add a signer.
• Add Signer is a separate screen state instead of always appearing above the list.
• File import now uses an upload/file icon, paste uses the clipboard icon, and QR scan uses the scanner icon.
• Empty clipboard paste now shows a clear error instead of doing nothing.
• Applies the import icon cleanup to both Signers and Create Multisig.

Verification:

• ./gradlew compileDebugKotlin
• ./gradlew assembleDebug assembleRelease
• git diff --check