Add fast split-friendly GPU solver

- [ ] Update [ftvp](https://github.com/svaiter/ftvp) to support conda install https://github.com/svaiter/ftvp/issues/1
- [ ] Implement odd/even split objective
- [ ] (optional) implement PD-split strategy to solve it to have a baseline or compare the difference in value function with a regular isotropic TV

Start by reviewing the ftvp project and its linked installation issue to understand the solver integration and conda support. Define the odd/even split objective, then assess whether the optional PD-split strategy can provide a baseline or value-function comparison against regular isotropic TV. Done means the requested solver support and objective are implemented and benchmarkable.

Written by the indexing model from the issue text.