fix(ui): keep Transfer modal fields and actions inside the dialog

[zheli]

Summary

• Cherry-pick of 44edcc3 from feat(campaign): light UI redesign, vitals, and share watermark #301 so main gets the Transfer modal overflow fix without waiting on the campaign redesign.
• Long party labels were expanding the form past the fixed modal width, so inputs and the Transfer button painted outside the panel.
• Containment styles on ModalShell, PartyPicker, form fields, and checkbox labels keep content inside the dialog.

Test plan

• Open Tokens → Transfer with long party labels selected
• Confirm From/To pickers, amount fields, and Transfer/Cancel stay inside the dialog
• Confirm coin-selection preview and auto-accept/atomic checkbox text wrap instead of overflowing
• Resize the window narrowly and confirm the modal scrolls within the viewport