Extract review logic into bot_actions module

Move `exec_review`, `download_git_diff`, and review formatting
to a new `bot_actions::review` module. Update the review flow to
post inline review comments via the Gitea API and simplify the
comment markdown to a summary. Add diff formatting that
preprocesses added lines with line numbers for the LLM prompt.

src/gitea.rs

@@ -3,7 +3,10 @@ use std::time::Duration;
 use serde::Deserialize;
 use serde_json::{Value, json};
 
-use crate::errors::AppError;
+use crate::{
+    bot::{ReviewItem, ReviewResult},
+    errors::AppError,
+};
 
 pub struct GiteaAPI {
     base_url: String,
@@ -80,6 +83,52 @@ impl GiteaAPI {
 
         Ok(())
     }
+
+    pub async fn post_pull_request_review(
+        &self,
+        review_result: &ReviewResult,
+        full_name: &str,
+        index: u64,
+    ) -> anyhow::Result<()> {
+        let url = format!(
+            "{}/api/v1/repos/{}/pulls/{}/reviews",
+            self.base_url, full_name, index
+        );
+
+        let comments = &&review_result
+            .reviews
+            .iter()
+            .filter(|r| r.line.is_some())
+            .map(|r| {
+                let path = r.filename.clone();
+                let line = r.line.unwrap_or(0);
+                let body = r.message.clone();
+
+                json!({
+                    "path": path,
+                    "new_position": line,
+                    "body": body
+                })
+            })
+            .collect::<Vec<_>>();
+
+        let res = self
+            .client
+            .post(url)
+            .json(&json!({
+                "event": "COMMENT",
+                "body": review_result.comment,
+                "comments": comments
+            }))
+            .send()
+            .await?;
+
+        if !res.status().is_success() {
+            return Err(anyhow::anyhow!("Failed to post review: {}", res.status()));
+        }
+
+        Ok(())
+    }
 }
 
 #[derive(Debug)]