GPS Bike Route Tracker

I need a straightforward mobile app whose sole job is to guide cyclists from A to B with live GPS navigation. Think of it as a lean companion that locks onto a chosen destination, maps the optimal bike-friendly route, and keeps the path clearly visible on-screen while I ride.

Key scope
• Platforms: iOS and Android (a single code-base with React Native, Flutter, or another cross-platform stack is fine).
• Mapping engine: Google Maps, Mapbox, or the native SDK—whichever lets you deliver turn-by-turn cycling directions with minimal latency.
• Core workflow: start ride → allow location permissions → display moving map with current location, distance remaining, and upcoming turn cues.
• No account system, performance analytics, or ride history in this first release; the app should open fast and stay focused on navigation only.

Deliverables
1. Source code and build instructions.
2. Release-ready APK / IPA files suitable for TestFlight or internal testing.
3. A brief README explaining how to update map keys and publish to the stores.

Acceptance criteria
• GPS lock within five seconds in normal outdoor conditions.
• Map refresh rate smooth at 30 fps on mid-range devices.
• Navigation remains accurate when the screen is off and audio cues are active.

Once the MVP is rock-solid we can discuss adding route history and performance stats, but for now I want the cleanest, most reliable GPS bike navigation experience possible.