[Enhancement] Replace BCG scheme with conservative advection for log-conformation tensor

## Overview
Currently using Bell-Collela-Glaz (BCG) scheme for log-conformation tensor advection. Proposal to evaluate and potentially implement a conservative form using VoF color function transport method.

## Related Issues
- #6 [Enhancement] Bound conformation tensor fields inside one of the fluids

This enhancement is closely related to issue #6, as both deal with the handling of conformation tensor fields. The conservative form implementation could potentially help with maintaining proper bounds on the tensor fields.

## Proposed Changes

### 1. Implementation Investigation
- [ ] Study conservative form implementation in `navier-stokes/conserving.h`
- [ ] Analyze compatibility with log-conformation tensor transport
- [ ] Evaluate VoF color function transport method integration
- [ ] Document potential impacts on numerical stability

### 2. Performance Analysis
- [ ] Benchmark current BCG implementation
- [ ] Implement test cases for conservative form
- [ ] Compare performance metrics:
- Computational cost
- Memory usage
- Numerical accuracy
- Stability characteristics
- Conservation properties

### 3. VoF Integration
- [ ] Design VoF color function transport integration
- [ ] Test boundary condition handling
- [ ] Evaluate impact on multi-phase simulations
- [ ] Document any limitations or constraints

## Technical Considerations
- Impact on existing simulations
- Compatibility with 3D implementation
- Integration with current tensor field calculations
- Effect on numerical stability
- Conservation properties validation

## Expected Benefits
- Improved conservation properties
- Potentially better stability
- More consistent behavior with VoF method
- Better handling of tensor field boundaries

## Implementation Strategy
1. Create test implementation branch
2. Develop prototype using simple test cases
3. Compare results with current implementation
4. Document performance differences
5. Make recommendation for full implementation

## Labels
- enhancement
- performance
- numerical-methods
- help wanted

## References
- `navier-stokes/conserving.h`
- Current BCG implementation
- Related research papers (to be added)