feat: add FetchUrlTool with proxy support and cross-OS path sanitization

- Implement native FetchUrlTool using reqwest for HTTP fetching, which respects HTTP_PROXY, HTTPS_PROXY, and NO_PROXY natively.
- Introduce sanitize_path in utils to bidirectionally handle Windows/WSL path mapping, applying it to various search/git handlers.
- Update .gitignore to exclude mcp_store.redb and tantivy_index.

server/src/handlers/http.rs

@@ -0,0 +1,138 @@
+use crate::router::McpTool;
+use crate::state::MemoryState;
+use crate::tools::FetchUrlTool;
+use async_trait::async_trait;
+use reqwest::Client;
+use serde_json::Value;
+use std::sync::Arc;
+
+pub struct FetchUrlHandler;
+
+#[async_trait]
+impl McpTool for FetchUrlHandler {
+    fn name(&self) -> &'static str {
+        "fetch_url"
+    }
+
+    fn schema(&self) -> Value {
+        crate::mcp::tool_def::<FetchUrlTool>(
+            "fetch_url",
+            "Fetch content from a URL via an HTTP GET request natively (supports proxy config via environment variables: HTTP_PROXY, HTTPS_PROXY, NO_PROXY)",
+        )
+    }
+
+    async fn execute(&self, args: Value, _state: Arc<MemoryState>) -> crate::error::Result<String> {
+        let req: FetchUrlTool = serde_json::from_value(args).map_err(|e| {
+            crate::error::AppError::BadRequest(format!(
+                "Schema validation failed. Your JSON arguments do not match the expected tool schema: {}",
+                e
+            ))
+        })?;
+
+        let mut client_builder = Client::builder();
+
+        // Add optional user agent
+        if let Some(ua) = req.user_agent {
+            client_builder = client_builder.user_agent(ua);
+        } else {
+            client_builder = client_builder.user_agent("mcp-memory-server/1.0");
+        }
+
+        // Reqwest automatically uses HTTP_PROXY, HTTPS_PROXY, NO_PROXY 
+        // environment variables by default, so we don't need to manually
+        // extract and apply them, the builder handles it.
+
+        let client = client_builder.build().map_err(|e| {
+            crate::error::AppError::Internal(format!("Failed to build HTTP client: {}", e))
+        })?;
+
+        let res = client.get(&req.url).send().await.map_err(|e| {
+            crate::error::AppError::Internal(format!("HTTP request to {} failed: {}", req.url, e))
+        })?;
+
+        let status = res.status();
+        let content = res.text().await.map_err(|e| {
+            crate::error::AppError::Internal(format!("Failed to read response body: {}", e))
+        })?;
+
+        if !status.is_success() {
+            return Ok(format!(
+                "HTTP Error: {} {}\n\nResponse Body:\n{}",
+                status.as_u16(),
+                status.canonical_reason().unwrap_or("Unknown"),
+                content
+            ));
+        }
+
+        Ok(content)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use axum::{routing::get, Router};
+    use tokio::net::TcpListener;
+
+    async fn spawn_test_server() -> String {
+        let app = Router::new()
+            .route("/test", get(|| async { "Hello, World!" }))
+            .route(
+                "/not_found",
+                get(|| async {
+                    (
+                        axum::http::StatusCode::NOT_FOUND,
+                        "Not Found Error",
+                    )
+                }),
+            );
+
+        let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let port = listener.local_addr().unwrap().port();
+        
+        tokio::spawn(async move {
+            axum::serve(listener, app).await.unwrap();
+        });
+
+        format!("http://127.0.0.1:{}", port)
+    }
+
+    #[tokio::test]
+    async fn test_fetch_url_success() {
+        let base_url = spawn_test_server().await;
+        let handler = FetchUrlHandler;
+        let url = format!("{}/test", base_url);
+
+        let res = handler
+            .execute(
+                serde_json::json!({
+                    "url": url
+                }),
+                Arc::new(MemoryState::new("")),
+            )
+            .await
+            .unwrap();
+
+        assert_eq!(res, "Hello, World!");
+    }
+
+    #[tokio::test]
+    async fn test_fetch_url_not_found() {
+        let base_url = spawn_test_server().await;
+        let handler = FetchUrlHandler;
+        let url = format!("{}/not_found", base_url);
+
+        let res = handler
+            .execute(
+                serde_json::json!({
+                    "url": url
+                }),
+                Arc::new(MemoryState::new("")),
+            )
+            .await
+            .unwrap();
+
+        assert!(res.contains("HTTP Error: 404 Not Found"));
+        assert!(res.contains("Not Found Error"));
+    }
+}