feat: add dynamic high-slippage warning banner with two-tier alert (Closes #111)

[waterWang]

Summary

Adds a dynamic high-slippage warning banner to the slippage settings popover, implementing the requirements from issue #111.

Changes

1. Lowered warning threshold

• Changed SLIPPAGE_WARNING_THRESHOLD from 5 to 2 — users now see a warning when slippage exceeds 2%.

2. Two-tier warning styling

• Amber/yellow (2-10%): High slippage warning — explains MEV sandwich attack risk and poor execution prices
• Red (>10%): Extreme slippage — high risk — warns of near-total fund loss

3. Improved warning text

• 2-10%: "Setting slippage above 2% puts you at risk of sandwich attacks and poor execution prices. Consider a lower value."

• 10%: "Setting slippage above 10% exposes you to extreme MEV sandwich attacks and near-total loss of funds. Consider a much lower value."

4. Tests

• Added unit tests for the updated constants and isSlippageRisky function with the new 2% threshold

Acceptance Criteria Fulfilled

• Warning message appears instantly when slippage > 2%
• The warning clearly explains the risk of MEV attacks/bad execution prices
• UI prevents confirming a slippage > 50% (already implemented)

[Lakes41]

This PR cannot be merged automatically because it has merge conflicts.

Please update the branch with the latest base branch and resolve the conflicts.

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