Add Copy/Move to context menu actions using Gtk.FileChooserNative

[Twilight0]

This PR introduces a standalone project adding two essential context menu actions to Nemo: Copy to... and Move to.... These actions allow users to copy or move selected files and folders to a destination chosen via the system's native folder picker.

Features

• Multi-Selection Support: Fully works for multiple selected files or folders of any mime type.
• Modern Desktop Integration: Uses Gtk.FileChooserNative to trigger the file picking dialog. This ensures native look-and-feel matching the active Cinnamon theme and provides compatibility with modern app sandboxing (e.g. Flatpaks using XDG Desktop Portals).
• Location Persistence: Automatically remembers and persists the last destination folder selected for each action (saved separately in ~/.config/dory/last_copy_location.txt and last_move_location.txt). If the folder is not found or is missing, it safely falls back to the user's Home directory.
• Non-Blocking Operation: Long running operations (e.g. copying large directories) run in a background thread to prevent UI freezing. A responsive progress dialog with a spinner and pulsing bar is displayed.
• Smart Name-Collision Resolution: If a target file or folder already exists at the destination, the action automatically appends a numeric counter suffix (e.g., File (1).txt) rather than failing or silently overwriting data.
• Error Handling: Displays descriptive error dialogs in case of failures (e.g. permission issues or out-of-disk-space warnings).
• Upstream-Compliant Design: Avoids deprecated or forbidden Nemo/Cinnamon APIs and is fully validated via the upstream repository's validate-spice checks.

---

File Structure

copy-move-to@twilight0/
├── info.json
├── CHANGELOG.md
├── README.md
├── copy-move-to@twilight0.nemo_action.in
├── move-to@twilight0.nemo_action.in
└── files/
    └── copy-move-to@twilight0/
        ├── copy_move_action.py
        ├── metadata.json
        └── icon.png

How to Test

1. Copy the copy-move-to@twilight0 directory to ~/.local/share/nemo/actions/.
2. Right-click any file or folder in Nemo/Dory.
3. Select Copy to... or Move to... from the context menu.
4. Select a destination folder using the native file chooser.
5. Verify the files are correctly moved/copied, and that the last folder is remembered for subsequent actions.

[mtwebster]

Nemo already has copy/move-to context menu items.

Unless you plan on packaging nemo, or your 'fork', as a Flatpak (a bad idea), the 'modern desktop integration' argument is makes no sense, either. edit: not accurate, sorry.

[Twilight0]

Native option includes an additional step, while this does not. Also this saves last location.