feat: Assigning hotkeys to actions and quicklinks

[ChisomUma]

This PR provides a requested feature in #235

it adds a feature to assign global hotkeys to custom shell commands (Quicklinks), giving RustCast a Raycast-like shortcut functionality.

Users can now configure global keyboard shortcuts for any [[shells]] item in their config.toml. When a shortcut is triggered, RustCast immediately executes the shell command in the background (e.g. launching an app or opening a URL) without requiring the user to open the RustCast search window.

How to Test
Open your RustCast configuration file at ~/.config/rustcast/config.toml.
Ensure there are no empty shells = [] declarations floating at the top of the file.
Add a custom mapped shell command to the bottom:

e.g

[[shells]]
alias = "Launch GitHub"
alias_lc = "github"
command = "open https://github.com"
hotkey = "CTRL+SHIFT+G"

[[shells]]
alias = "Launch VS Code"
alias_lc = "vscode"
command = "open -a 'Visual Studio Code'"
hotkey = "CTRL+SHIFT+V"

[[shells]]
alias = "Toggle Dark Mode"
alias_lc = "darkmode"
command = "osascript -e 'tell app \"System Events\" to tell appearance preferences to set dark mode to not dark mode'"
hotkey = "CTRL+SHIFT+D"

[[shells]]
alias = "Open Downloads"
alias_lc = "downloads"
command = "open ~/Downloads"
hotkey = "CTRL+SHIFT+M"

Below is a screen record:

screen-capture.1.online-video-cutter.com.1.mp4

[unsecretised]

Hi @ChisomUma. Thank you for yout PR!
Can I ask you to update this branch from #234 It adds a settings UI for shell commands as well, so while thats getting reviewed and merged, adding this branch will be simple! Until then, I'll review the code.

If you're comfortable, could you join the discord server to be able to communicate with the developers better?

[unsecretised]

LGTM

[unsecretised]

Or ykw, i'll add it myself