terms: per-term installer visibility toggles + universal delete (v0.3.4)

- _meta.json: customLabels -> terms.{label,showInInstaller,showInInstallerRp}
- Drop builtin protection; any term kind can be deleted/added/toggled
- New public route /manifest/terms/<pack>/index.json for installer term lists
- Installers fetch terms:list dynamically; skip agreement step if list empty
- Term editor: 2 visibility checkboxes (설치기 / 리소스팩 설치기), multi-select
- Migration from old schema preserves custom labels (default: visible in both)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

locales/server/ko-kr.json

@@ -160,7 +160,11 @@
     "slashQuote": "인용",
     "slashCode": "코드",
     "leaveConfirm": "저장하지 않은 변경사항이 있습니다.\n저장 없이 이 페이지를 떠나시겠습니까?",
-    "builtinBadge": "기본",
+    "visibilityHeading": "표시 대상 (중복 선택 가능)",
+    "visibilityInstaller": "설치기에 표시",
+    "visibilityInstallerRp": "리소스팩 설치기에 표시",
+    "visibilityInstallerShort": "설치기",
+    "visibilityInstallerRpShort": "리소스팩",
     "addHeading": "약관 추가",
     "kindLabel": "식별자",
     "kindPlaceholder": "예: privacy",