Add native calendar solver package

[blackopsrepl]

This adds the package for Omarchy’s native calendar planner solver.

It builds the tagged v0.1.1 Rust adapter from a checksum-pinned source archive
and installs one executable at /usr/bin/omarchy-calendar-solver. The package
ships the adapter’s MIT license, SolverForge’s Apache 2.0 license, and NOTICE;
it does not add Cargo, a service, configuration, or a desktop entry to users’
systems.

The adapter is here:
https://github.com/blackopsrepl/omarchy-calendar-solver/tree/v0.1.1

The companion Omarchy change is here:
omacom/omarchy#10215

Verification:

• makepkg --printsrcinfo --nodeps
• Clean makepkg --nodeps --cleanbuild --clean from the tagged archive
• The resulting package contains only the solver binary, documentation, and
  required license notices.

[Chessing234]

pkbuild looks fine — pinned tarball, sha256, no curl|bash.