Integrate OpenRouter for AI-powered code review

Add openrouter-rs dependency, review prompt, and markdown formatting.
Update comment API to accept dynamic body. Adjust devcontainer for
podman compatibility.

Cargo.toml

@@ -8,6 +8,7 @@ reqwest = { version = "0.13", features = ["json"] }
 tokio = { version = "1.52", features = ["full"] }
 serde_json = "1.0"
 serde = { version = "1.0", features = ["derive"] }
+openrouter-rs = "0.10"
 dotenvy = "0.15"
 axum = "0.8"
 anyhow = "1.0"
@@ -16,4 +17,4 @@ hmac = "0.13"
 sha2 = "0.11"
 hex = "0.4"
 subtle = "2.6"
-bytes = "1.11"
+bytes = "1.11"