enhance(frontend): テーマの適用管理を改善 (#17376)

* wip

* add test

* use themeManager.currentCompiledTheme for obtaining theme variables / reduce getComputedStyle usage

* fix

* fix: better error handling on theme installation

* Update Changelog

* chore: remove frontend-shared builds as it is currently working as a stub package

* fix: broken lockfile

* fix

* fix lint

* fix

scripts/dev.mjs

@@ -70,12 +70,6 @@ execa('pnpm', ['--filter', 'backend', 'dev'], {
 	stderr: process.stderr,
 });
 
-execa('pnpm', ['--filter', 'frontend-shared', 'watch', '--no-clean'], {
-	cwd: _dirname + '/../',
-	stdout: process.stdout,
-	stderr: process.stderr,
-});
-
 execa('pnpm', ['--filter', 'frontend', 'watch'], {
 	cwd: _dirname + '/../',
 	stdout: process.stdout,