refactor: adopt FilledButtonStyle across more screens

[raulriera]

Summary

• Replaces CodeButton(style: .filled) with Button + .buttonStyle(.filled) in 10 screens
• Replaces CodeButton(style: .filledCustom) in FundingSelectionSheet by moving the icon into the button label

Screens updated

• CurrencyInfoScreen ("Buy")
• CurrencyInfoErrorView ("OK")
• FundingSelectionSheet ("USD Reserves", "Solana USDC With Phantom")
• ForceUpgradeScreen ("Update Now")
• TransactionDetailsModal ("Cancel Send")
• PermissionScreen (dynamic title)
• AccessKeyHelpScreen ("Open Photos")
• OnrampSuccessScreen ("OK")
• VerifyInfoScreen ("Next")
• ModalCashReceived (dynamic title)

Test plan

• Verify all updated screens render buttons correctly
• Verify press states animate with the 0.7 opacity transition
• Verify FundingSelectionSheet Phantom button still shows icon inline with text