Add rate limit indication and prevention for rapid transaction signing requests

[savvyer]

Problem

When users sign multiple transactions quickly (especially in batch), the extension can reject subsequent requests without clear feedback. This leads to:

• Silent failures that look like user rejections
• Poor UX with no explanation
• Extra work for dApp developers to add delays/retries
• Confusion about whether the user rejected or the extension rate-limited

Current Behavior

• User initiates signing for multiple transactions (e.g., 3 transactions)
• User approves quickly in the extension
• First transaction signs successfully
• Subsequent transactions are rejected by the extension
• dApp receives rejection errors without clear cause
• No indication in the extension UI that rate limiting occurred

Expected Behavior

• Show a rate limit indicator in the extension UI when multiple signing requests arrive quickly
• Display a message like "Please wait X seconds before signing the next transaction" or "Signing too quickly, please wait..."
• Optionally: prevent/disable the sign button temporarily to avoid rate limit errors

Recording

Transaction with nonce 84 is signed.
Next transaction with nonce 85 is rejected due to rate limiting.

Screen.Recording.2026-01-14.at.2.00.34.PM.mov