feat: make settings content scrollable

[samdaw13]

Summary

• Wraps the rotor and plugboard section of the Settings screen in a ScrollView so users can scroll through their configuration when many plugboard cables are added
• The bottom action buttons (Clear, Randomize, Encrypt Message) remain fixed and are always accessible

Test plan

• Add 5+ plugboard cables and verify the settings area scrolls without covering the buttons
• Verify the Clear, Randomize, and Encrypt Message buttons remain visible and tappable at all times
• Verify existing rotor and plugboard functionality is unaffected

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