feat: Create a "Share on X" social post-swap modal

[AlAfiz]

Description

Growth is critical for Wave 3. When a user successfully completes a trade, we should encourage them to brag about it.
We need a simple post-trade success modal that includes a "Share on X (Twitter)" button.
When clicked, it should open a pre-populated tweet window with a message and a link back to TradeFlow.
This is a standard organic marketing tactic used by major Web3 applications.

Requirements

• Create a TradeSuccessModal.tsx component that triggers after the isSubmitting state resolves successfully.
• Add a large green checkmark and text: "Swap Successful!".
• Add a secondary button with the X/Twitter logo.
• Use a standard href="https://twitter.com/intent/tweet?text=..." link to prepopulate a message like: "Just swapped XLM on TradeFlow Beta! 🚀".