Implement Kitty graphics protocol for background image rendering

- Added `kitty_gfx` module to handle loading, scaling, and displaying background images using the Kitty graphics protocol.
- Integrated background image handling into the main application loop, allowing dynamic updates based on configuration.
- Enhanced terminal rendering to support transparent backgrounds when a Kitty image is active.
- Updated IPC server to manage client connections and messages, including handling background image settings.
- Modified `PtyTerminal` to accept additional environment variables during shell spawning.
- Improved rendering logic to support popup dialogs and terminal background color customization.

Cargo.toml

@@ -11,7 +11,11 @@ path = "src/main.rs"
 crossterm = { version = "0.28", features = ["event-stream"] }
 ratatui = "0.29"
 serde = { version = "1", features = ["derive"] }
+serde_json = "1"
 toml = "0.8"
+toml_edit = "0.22"
 portable-pty = "0.8"
 vt100 = "0.15"
 anyhow = "1"
+image = { version = "0.25", default-features = false, features = ["jpeg", "png", "gif", "bmp", "webp"] }
+libc = "0.2"