Remove unused files: old UI, build scripts, fonts, test files

Remove old widget-based Python UI (replaced by QML), unused build
scripts, NL/variable/webfont variants, old shaders, PNG icons
(replaced by SVGs), and standalone test files. Add build.bat and
build.spec for the bootstrapper build system.

.gitignore

@@ -10,13 +10,16 @@ env/
 # Distribution / Build
 dist/
 build/
-*.spec
-_unused_files/
 runtime/
 
+# Trash / Unused
+_trash/
+_unused_files/
+
 # IDEs
 .vscode/
 .idea/
+.claude/
 
 # Application Specific
 models/