Flutter Google Navigation Integration

My Flutter app already has a working Maps view and a solid UI foundation, but the actual navigation layer is still missing. I now need the Google Navigation Flutter package woven cleanly into the existing codebase so users can:

• receive real-time, turn-by-turn guidance, and
• set custom waypoints along a route.

The same experience must work on both iOS and Android without platform-specific quirks. All routing, voice-over prompts, and recalculations should appear inside the current Maps view so the transition feels native to the rest of the app.

I will hand over the repository and walk you through the current architecture once we agree on the implementation plan. Your job ends when I can:

• pull the branch, run flutter run on either platform,
• choose start / end points (plus optional waypoints) from the existing UI,
• watch navigation begin with smooth updates, and
• see no regressions in previously working screens.

Please keep your code well commented, follow Flutter best practices, and outline any new permissions or configuration steps in a short README so I can reproduce the build in one go.