Add Déjà Dup Backups extension

extensions/deja-dup/.gitignore

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+node_modules/
+dist/
+*.log
+.DS_Store
+vicinae-env.d.ts

extensions/deja-dup/CHANGELOG.md

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+# Déjà Dup Backups Changelog
+
+### Friday, July 17, 2026
+
+- Initial release.
+- Browse snapshots and restore individual files or folders.
+- Fast, offline file search backed by a one-time local index (with optional background indexing).
+- Back Up Now and Backup Status commands.
+- Backends: local folder, removable drive, network server (SMB/SFTP/WebDAV/Nextcloud),
+  Google Drive, OneDrive, and rclone remotes.
+- Native, Snap and (best-effort) Flatpak installations, with manual overrides in preferences.

extensions/deja-dup/LICENSE

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+MIT License
+
+Copyright (c) 2026 samvoelzke
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

extensions/deja-dup/README.md

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+# Déjà Dup Backups
+
+Browse, search and restore files from your [Déjà Dup](https://wiki.gnome.org/Apps/DejaDup)
+backups directly from [Vicinae](https://vicinae.com) — without opening the GUI.
+
+Déjà Dup 45+ stores its backups as a [restic](https://restic.net) repository. This extension
+talks to that repository read-only, reusing the credentials Déjà Dup already saved, so there is
+nothing to configure.
+
+## Commands
+
+- **Browse Backup** — list snapshots, drill into the file tree, preview a file, and restore
+  individual files or folders (to their original location or anywhere you choose).
+- **Search Backup Files** — build a small local index of your latest backup once, then search it
+  instantly and offline (searching a cloud backup file-by-file is far too slow otherwise).
+- **Back Up Now** — start a fresh backup, and see the last backup, destination, schedule and
+  included/excluded paths.
+
+## Supported backends
+
+| Backend | Status | Notes |
+| --- | --- | --- |
+| Local folder | ✅ | |
+| Removable drive | ✅ | drive must be connected/mounted |
+| Network server | ✅ | SMB, SFTP, WebDAV/Nextcloud — mount it once in Files first |
+| Google Drive | ✅ | |
+| OneDrive (Personal) | ✅ | |
+| rclone remote | ✅ | uses your `rclone.conf` |
+
+Backups made with **duplicity** or **borg** (older Déjà Dup, or an explicit choice) are not
+readable by this extension — only restic backups are.
+
+## Installation flavor (native / Flatpak / Snap)
+
+The extension auto-detects how Déjà Dup is installed and adapts:
+
+- **Native** (system package) and **Snap** (classic confinement) — full support, all backends.
+- **Flatpak** — Déjà Dup's config and passwords live in the app's sandbox, unreachable from
+  outside. Local, network and drive backups work if you enter your backup password under
+  **Backup Password** in the extension settings; cloud backups (Drive/OneDrive/rclone) keep their
+  tokens in the sandboxed keyring and need the native or Snap Déjà Dup.
+
+You can override the detected flavor and set custom binary paths / the backup password under the
+extension's preferences (⌘/Ctrl+,) if your setup is unusual.
+
+## Requirements
+
+- Déjà Dup with a restic backup already configured and run at least once
+- `restic` and (for cloud backends) `rclone` available on `PATH`
+- The GNOME keyring unlocked (open Déjà Dup once after login so the password/token are available)
+
+All access is **read-only** on the repository (`restic --no-lock`); the extension never prunes,
+forgets or writes to your backup. Restores only ever create new files in the target directory.
+
+## How it works
+
+Configuration (backend, target folder, schedule) is read from GSettings
+(`org.gnome.DejaDup`). The repository password comes from the keyring
+(`secret-tool lookup owner deja-dup type passphrase`). For Google Drive, Déjà Dup's own OAuth
+refresh token is read from the keyring and exchanged for a short-lived access token, which is
+cached in the extension's support directory until it expires.
+
+## License
+
+MIT