Switch from direct libnotify to Tauri notification plugin once upstream issues are resolved

[ariyadey]

Currently, Capturist uses libnotify directly to send desktop notifications on Linux, rather than the Tauri notification plugin. The decision and technical reasons for this workaround are documented in src-tauri/src/ipc/commands.rs (see the send_notification function). This approach is suboptimal and error-prone.

Reasons to switch to the Tauri Notification plugin:

• The plugin is the officially supported way for notifications in Tauri, ensuring better integration and maintainability.
• Direct libnotify usage leads to platform-specific hacks and can break more easily across Linux desktop environments or future OS releases.
• Reduced dependency on external binaries and less risk of "notify-send not found" errors.
• Benefit from active community support, upstream fixes, and unified experience across platforms.
• Future-proofing: code using official plugins is more likely to remain compatible with Tauri software evolution.

Next steps:

• Monitor the status of upstream bugs for the Tauri notifications plugin (see: [bug] no notifications in gnome 46+ (eg fedora 41 and ubuntu 24.04) tauri-apps/plugins-workspace#2566).
• Switch to the plugin and remove the current libnotify solution once stable and compatible.