Refactor to Cargo Workspace (#129)

* Refactor project into a Cargo workspace with distinct packages

- Created a root `Cargo.toml` defining a workspace.
- Moved `src/types` and `src/utils` into a new `pwsp-lib` crate for shared logic.
- Split binaries into their own crates: `pwsp-daemon`, `pwsp-cli`, and `pwsp-gui`.
- Shifted all dependencies into `[workspace.dependencies]` for centralized version management.
- Updated import paths across all crates (e.g. from `pwsp::` to `pwsp_lib::`).
- Updated build scripts, GitHub actions, Flatpak manifest, and AUR PKGBUILD to support the new workspace structure.
- Ensured no core application logic was altered.

Co-authored-by: arabianq <55220741+arabianq@users.noreply.github.com>

* Fix cargo-deb build process in GitHub actions for workspace architecture

Co-authored-by: arabianq <55220741+arabianq@users.noreply.github.com>

* Fix cargo-deb asset discovery by using exact target/release paths

Co-authored-by: arabianq <55220741+arabianq@users.noreply.github.com>

* refactor deps in Cargo.toml files

* fix incorrect assets path

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Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>

pwsp-gui/assets/pwsp-gui.desktop

@@ -0,0 +1,9 @@
+[Desktop Entry]
+Name=PWSP (Soundpad)
+Comment=Let's you play audio files through you microphone
+Exec=/usr/bin/pwsp-gui %u
+Icon=pwsp
+Terminal=false
+Type=Application
+Categories=Audio
+MimeType=x-scheme-handler/soundpad;