feat: add Korean-English localization and light theme

Localize studio, curriculum, visualization and loading interfaces. Add persistent language and theme settings, refine module loading states, and normalize remote shell locales.

src/main/remoteShell.ts

@@ -0,0 +1,28 @@
+function quote(value: string): string {
+  return `'${value.replace(/'/g, `'"'"'`)}'`
+}
+
+// SSH may forward LANG/LC_* through the user's SendEnv configuration.
+// Undefined entries also remove inherited keys when merged by the command runner.
+export function remoteShellEnvironment(env: NodeJS.ProcessEnv): NodeJS.ProcessEnv {
+  const result = { ...env }
+  for (const key of Object.keys(result)) {
+    if (key === 'LANGUAGE' || key.startsWith('LC_')) result[key] = undefined
+  }
+  return { ...result, LANG: 'C', LC_ALL: 'C' }
+}
+
+export function remoteShellCommand(command: string): string {
+  const script = [
+    'selected_locale=C',
+    // Probe under C so an inherited, unavailable locale cannot break the probe.
+    'available_locales=$(locale -a 2>/dev/null) || available_locales=',
+    'for candidate in $available_locales; do',
+    '  case "$candidate" in C.utf8|C.UTF-8) selected_locale=$candidate; break ;;',
+    '    *utf8|*UTF-8|*utf-8) if [ "$selected_locale" = C ]; then selected_locale=$candidate; fi ;;',
+    '  esac',
+    'done',
+    `exec env LANG="$selected_locale" LC_ALL="$selected_locale" LANGUAGE=C /bin/bash --noprofile --norc -c ${quote(command)}`,
+  ].join('\n')
+  return `env LANG=C LC_ALL=C LANGUAGE=C /bin/sh -c ${quote(script)}`
+}