ux: unify Add Mint input — move paste into the URL field (match onboarding)

[callebtc]

Summary

The Add mint URL input differs between onboarding (first mint custom URL) and the in-wallet Add Mint sheet. Paste is a trailing control inside the field during onboarding, but a separate full-width link below the primary button in the wallet sheet. Align the wallet sheet with the tighter in-field paste pattern.

Platforms

• iOS
• Android

Current UI

Onboarding — custom mint row (trailing icon on field)

State	Trailing control
Empty	Paste (clipboard)
Non-empty	Add / commit (arrow)

• iOS: ios/CashuWallet/Views/Main/OnboardingView.swift — customMintInputRow
• Android: android/.../ui/onboarding/OnboardingScreen.kt — FirstMintFace trailing ContentPaste / ArrowCircleRight on CashuTextField

In-wallet Add Mint sheet (paste under primary CTA)

• Primary Add Mint button

• Ghost / text link “Paste URL from Clipboard” below it

• Trailing icon on field is QR scan, not paste

• iOS: ios/CashuWallet/Views/Mints/AddMintSheet.swift

• Android: android/.../ui/mints/AddMintSheet.kt

• Entry: MintsListView.swift / MintsScreen.kt

Expected

Same paste affordance as onboarding: paste control lives in/near the URL input (or both paste + scan as trailing actions), not a second link under the submit button.

Suggested direction

1. Move paste into the URL field row on AddMintSheet (both platforms).
2. Keep scan who/how it is (trailing scanner icon is fine; may use a small dual trailing layout on or under the field).
3. Optionally drop the bottom “Paste URL from clipboard” link once in-field paste exists.
4. Cross-check restore staging (Add | Paste | Nostr chips) — may stay different by design (multi-URL paste); document if intentional.