Remove obsolete lattice-preview GUI

[skilledwolf]

Summary

• remove the unmaintained wxPython/VTK lattice-preview GUI
• remove its launcher and private Python helper modules
• remove its CMake installation block and Debian install-manifest entry

Why

The feature was introduced in 2009 and last updated in 2016. Its launcher still relies on Python 2 syntax and contains broken environment-variable names (BUILDIDR and PHTHONPATH), while the GUI uses legacy wxPython APIs and has no dependency detection for wxPython or VTK. Ordinary non-wheel builds install it even when those runtime dependencies are unavailable.

Removing the feature as a unit is safer than retaining or modernizing its otherwise-unused tool/license.py helper.

Scope

The removal is self-contained: it deletes only the obsolete GUI, its private helpers, its build and installation rules, and its packaging-manifest entry.

Validation

• fresh minimal CMake configuration with Python, applications, examples, and tests disabled
• no remaining lattice-preview or helper-module references
• git diff --check

The commit includes [skip ci]; these removal-only changes were validated locally without starting CI.

[egull]

I'm ok with removing it but @wistaria is the author. Synge, should we fix it, rather than remove it?

[Ooolab]

I am ok with either keeping or removing the lattice-preview GUI. @vws100 pointed out another lattice drawing repo: https://github.com/ALPSim/latticegraph_designer , which I forked to our repo a while ago. It is working now, but we would need to do some work to include it in ALPS. @vws100 , could you weigh in on whether to keep/remove or include the other repo you found.

[skilledwolf]

Please note: PRs #107 and #111, #112 and #114 were stacked (only #107 was targeted into master). That was my bad, I'm rebasing them now, so we can land them independently for the release.

[egull]

Not getting anything from @wistaria . I propose we remove and reintroduce if Synge would like to have it updated. Happy to approve the PR.

[egull]

Approving removal. We can cycle back to this later to either modernize the code or integrate the other outside repo, but that's a decision for later.