feat(server-mode): native-like folder browser, a developer kept to their own folder, no password minimum

- Folder browser (the Browse fallback for a remote browser): back/forward/up,
  a clickable breadcrumb that becomes a path field (Ctrl+L), Places (Home,
  the user's workspaces, recent picks), a filter, Name/Modified columns,
  Show hidden and New folder. A click selects; a double-click or Enter
  opens a folder or picks a file; Backspace goes up; typing jumps to a name.
- GET /api/lanes/browse: `hidden=1` (never the dot entries at the top of a
  non-admin's own folder), each entry's `mtime`, the answer's `home`.
- POST /api/lanes/browse/mkdir: one plain folder name inside an existing
  folder; a non-admin only in their own folder, none in server mode without
  one; under S3 a member's folder is made as the member.
- scope.ownFolder falls back to server.conf's USERS_ROOT under S3, so a
  settings file without AGENTHUB_USERS_ROOT no longer opens the host's home
  to every developer.
- Passwords: any non-empty password is accepted (no 8-character minimum).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

client/src/i18n/locales/vi/lanes.json

@@ -42,6 +42,24 @@
   "browse.empty": "Thư mục này trống.",
   "browse.fileTitle": "Duyệt chọn tệp",
   "browse.select": "Chọn thư mục này",
+  "browse.back": "Quay lại (Alt+←)",
+  "browse.create": "Tạo",
+  "browse.editPath": "Gõ đường dẫn (Ctrl+L)",
+  "browse.filter": "Lọc…",
+  "browse.forward": "Tiến (Alt+→)",
+  "browse.hint": "Nháy đúp hoặc Enter để mở · Backspace để lên · gõ chữ để nhảy tới",
+  "browse.home": "Thư mục chính",
+  "browse.modified": "Ngày sửa",
+  "browse.name": "Tên",
+  "browse.newFolder": "Thư mục mới",
+  "browse.newFolderName": "Tên thư mục",
+  "browse.noMatch": "Không có mục nào khớp bộ lọc.",
+  "browse.places": "Vị trí",
+  "browse.recent": "Gần đây",
+  "browse.selectFile": "Chọn tệp",
+  "browse.showHidden": "Hiện mục ẩn",
+  "browse.up": "Lên một cấp (Backspace)",
+  "browse.workspaces": "Workspace",
   "browse.title": "Duyệt chọn thư mục",
   "changes.back": "Tất cả file",
   "changes.bin": "bin",