Web SDK: Improve error handling and error display

## Summary

Improve error handling across the web SDK to make debugging easier for developers.

### Tasks

- [ ] Add help to the worker serializer
- [ ] Replace panics with proper `Result` returns in model files (`note_filter`, `transaction_requests`)
- [ ] Expand hint coverage to more error variants (especially `InsufficientFunds`, `InvalidInputNotes`, prover errors)
- [ ] Use `{err}` (Display) instead of `{err:?}` (Debug) in places that use Debug format (e.g. `export.rs`)
- [ ] Better error display for MASM compilation errors

Look at the worker serializer, model files like note_filter and transaction_requests, and export.rs. Replace panics with Result returns, improve error formatting from Debug to Display, and expand hint coverage for specific error variants. Check MASM compilation error display. Run existing tests to ensure changes don't break functionality.

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