## 🚀 Add pure Rust Dictionary implementation

[Soroushsrd]

This PR starts the gradual replacement of quickfix-ffi with quickfix-native as discussed in #21.

What's included:

• ✅ Pure Rust Dictionary implementation
• ✅ Matches C++ QuickFIX API exactly
• ✅ Error handling with NativeError
• ✅ Type-safe key-value operations (string, int, double, bool, day-of-week)

Next steps:

• Full test coverage for implemented changes
• SessionID implementation
• Message/Header/Trailer types
• ...

[Soroushsrd]

Latest Update: SessionID Implementation ✅

Added pure Rust SessionID with:

• String parsing matching C++ fromString() logic
• Basic field types (BeginString, SenderCompID, TargetCompID)
• Test coverage
• Idiomatic Rust traits (Display, TryFrom)

What's included so far:

✅ Pure Rust Dictionary implementation
✅ SessionID implementation
✅ Basic field types
✅ Error handling with NativeError
✅ Type-safe operations matching C++ API

Working on next:

• More field types as needed
• Message/Header/Trailer types
• Coverage improvements

[Soroushsrd]

Changes Made

Core Message Infrastructure

• ✅ MessageOrder for proper FIX field ordering
• ✅ FieldMap for field storage and management
• ✅ Group support for repeating field groups

Next Steps

• Message, Header, Trailer implementations