Clean up compiler warnings and document Ollama/LiteLLM backends

Remove unused `any_docker_mcp()` function, add `#[allow(unused_imports)]`
and `#[allow(dead_code)]` annotations to suppress false-positive warnings.
Update README.md and HOW-TO-USE.md with Ollama and LiteLLM auth backend
documentation including best-effort compatibility notices.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/src-tauri/src/docker/mod.rs

@@ -4,8 +4,13 @@ pub mod image;
 pub mod exec;
 pub mod network;
 
+#[allow(unused_imports)]
 pub use client::*;
+#[allow(unused_imports)]
 pub use container::*;
+#[allow(unused_imports)]
 pub use image::*;
+#[allow(unused_imports)]
 pub use exec::*;
+#[allow(unused_imports)]
 pub use network::*;