chore(04-01): add Phase 4 deps and create splash module

- Add notify = "6.1", ansi-to-tui = "8.0", walkdir = "2.5" to Cargo.toml
- Create src/splash.rs with load_splash() using IntoText trait
- Add mod splash to main.rs module declarations
- Verified single ratatui-core v0.1.0 in dependency tree

Cargo.toml

@@ -12,3 +12,6 @@ clap = { version = "4.5", features = ["derive"] }
 pulldown-cmark = "0.13.1"
 syntect = { version = "5.3", default-features = false, features = ["default-fancy"] }
 syntect-tui = "3.0"
+notify = "6.1"
+ansi-to-tui = "8.0"
+walkdir = "2.5"