Add a precompilation workload using PrecompileTools.jl that precompiles
the most common entry points:
- FVMGeometry creation
- Dirichlet and Neumann boundary conditions
- BoundaryConditions combinations
- FVMProblem creation
- ODEProblem creation from FVMProblem
- jacobian_sparsity

Timing improvements (tested with Julia 1.10):

Before:
- Package load time: 1.046 seconds
- First FVMGeometry: 0.108 seconds
- First BoundaryConditions: 0.009 seconds
- First FVMProblem: 0.065 seconds
- First ODEProblem: 0.451 seconds
- Total TTFX: 0.633 seconds

After:
- Package load time: 1.068 seconds
- First FVMGeometry: ~0 seconds (99% improvement)
- First BoundaryConditions: ~0 seconds (99% improvement)
- First FVMProblem: 0.063 seconds (no change, expected due to user functions)
- First ODEProblem: 0.036 seconds (92% improvement)
- Total TTFX: 0.1 seconds (84% improvement)

Precompilation time increased from ~2s to ~3s, which is acceptable given
the TTFX improvements.

Note: No invalidations were found from this package. The few invalidations
detected during load come from dependencies (RecursiveArrayTools, SciMLBase).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>