Add Interactive Onboarding Tutorial

[google-labs-jules]

Implemented an interactive onboarding tutorial using a new Tutorial.jsx component.

• Added a Tutorial component that uses a portal and box-shadow overlay to guide users through the app's features (Records, Map, Stats, Login).
• Added id attributes to key UI elements in RailRound.jsx and LoginModal.jsx to allow the tutorial to target them.
• Implemented state logic to automatically advance steps based on user interaction (e.g., switching tabs, opening modals).
• Added persistence for skipping the tutorial via localStorage.
• Updated RailRound.jsx to integrate the tutorial component.
• Added a verification script to ensure structural correctness.

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PR created automatically by Jules for task 1944810006170845098 started by @OsakaLOOP

[google-labs-jules]

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