Feat: "Add to Home screen" option to create folder shortcuts with deep link

[Lightz2002]

• Adds an "Add to Home screen" action for folders that pins a launcher shortcut,
  deep-linking straight into that folder when tapped.

Changes

• Add ADD_TO_HOME_SCREEN to FileMenuOption and wire it into the file actions menu
  (action_add_to_home) with a new icon; only shown for single-selected folders via
  FilterFileMenuOptionsUseCase
• New AddToHomeScreenDialogFragment: pre-filled, editable shortcut name with validation
  (empty name, max filename length, forbidden characters)
• New FolderShortcutHelper: creates a pinned shortcut via ShortcutManager (API 26+),
  embedding the folder's remote ID, remote path, and space ID in the intent
• FileDisplayActivity handles the new OPEN_SHORTCUT action: resolves the folder by
  remote path + space ID from local storage and navigates directly into it; extras are
  consumed after handling; shows an error snackbar if the folder no longer exists locally

Notes

• Devices below API 26 show a toast instead of creating a shortcut
• Shortcut opens in All Files view regardless of the last used file list option

Testing

• Long-press/overflow menu on a folder → "Add to Home screen" → confirm → pin the shortcut
• Tap the shortcut → app opens directly inside the target folder
• Rename the shortcut in the dialog; verify empty names / forbidden chars are rejected
• Delete the folder, then tap the shortcut → error message shown