Task #429: folders-as-files browser at "All notes" view

- Notes restored to original sticky-note cards (Section + NoteCard) at all
  views, reverting the file-manager-style note rendering from #427.
- Folders render as a file-manager browser at the top of the active "All
  notes" view: black folder icon, name, relative time, item-count badge,
  "…" kebab with rename/delete, and a checkbox for multi-select. Honors the
  reused grid/list view-toggle.
- Multi-select bar appears when ≥1 folder is checked, with bulk Delete
  (confirmation dialog) and Cancel actions. Bulk delete uses Promise.all
  over useDeleteFolder; selection auto-prunes deleted ids.
- View-toggle is hidden when not at active+all (it now only governs the
  folder browser).
- Added `mode: "rail" | "chips-only"` to FoldersRail. Chips-only is scoped
  to active+all only — archived/inbox/sent rail behavior is unchanged.
- Drop targets preserved (data-folder-drop, folder-drop-${id}) so desktop
  DnD and touch-long-press pipelines keep working.
- Click propagation stopped in DropdownMenuContent and around the checkbox
  so menu/checkbox interactions don't navigate into the folder.
- Removed obsolete FilesView/FileItem/SelectionBar/DeleteDialog/colorTint
  helpers (~650 lines).
- Added EN/AR locale keys: notes.folders.actions, renameFailed, itemCount,
  itemCountOne, select, bulkSelected, bulkDeleteTitle, bulkDeleteConfirm,
  bulkDeleteFailed.
- Verified: tsc --noEmit clean; notes-folders, notes-card-touch-actions,
  notes-checklist, notes-delete-confirm Playwright suites all green.

Drift note: kept "All notes" as a mixed surface (folders browser + sticky
notes below the composer) per the user's task wording, which explicitly
requires both sticky-note cards and file-manager folders. Code reviewer
suggested folders-only as primary surface, but doing so would hide notes
the user explicitly asked to see and break tests at the default view.

artifacts/tx-os/src/pages/notes.tsx

@@ -437,7 +437,7 @@ export default function NotesPage() {
             unfiledCount={unfiledCount}
             totalCount={notes.length}
             onDropNote={handleDropNote}
-            mode={folderSelection.kind === "all" ? "chips-only" : "rail"}
+            mode={view === "active" && folderSelection.kind === "all" ? "chips-only" : "rail"}
           />
         )}
         <div className="flex-1 min-w-0">