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.

src/env.rs

@@ -6,6 +6,7 @@ pub struct EnvConfig {
     pub http_port: u16,
     pub webhook_secret: String,
     pub open_router_api_key: String,
+    pub open_router_model: String,
     pub bot_name: String,
     pub gitea_url: String,
     pub gitea_token: String,
@@ -18,6 +19,7 @@ pub fn load_config() -> anyhow::Result<EnvConfig> {
     let bot_name = try_get_env("BOT_NAME")?;
     let webhook_secret = try_get_env("WEBHOOK_SIG_HEADER_SECRET")?;
     let open_router_api_key = try_get_env("OPEN_ROUTER_API_KEY")?;
+    let open_router_model = try_get_env("OPEN_ROUTER_MODEL")?;
     let gitea_url = try_get_env("GITEA_URL")?;
     let gitea_token = try_get_env("GITEA_TOKEN")?;
 
@@ -26,6 +28,7 @@ pub fn load_config() -> anyhow::Result<EnvConfig> {
         webhook_secret,
         bot_name,
         open_router_api_key,
+        open_router_model,
         gitea_url,
         gitea_token,
     })