[Feature] IMU complentary filter for sensor fusion

**Problem statement: what's wrong with it?**
IMU's accel and IMU's gyro sensors need to be fused

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**Proposed solutions: describe alternatives you've considered**
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**Additional context**
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No source file, test, entry point, filter parameters, or acceptance criteria are named. Start by locating the C code that reads the IMU accelerometer and gyroscope, then clarify the complementary-filter behavior and validation criteria with maintainers. Done means the agreed fused sensor output is implemented and validated.

Written by the indexing model from the issue text.