feat(tui): add usage overlay and sidebar for displaying usage statistics and tasks

feat(tui): implement status bar with connection and turn state indicators
feat(tui): create workflow panel for agent status and progress visualization
feat(web): introduce web frontend interface with static file serving
feat(ws): add WebSocket interface for real-time communication and session management

apps/infrastructure/src/middleware/rate_limit.rs

@@ -0,0 +1,60 @@
+//! Simple in-memory rate limiter for Axum.
+
+use std::collections::HashMap;
+use std::sync::Mutex;
+
+/// In-memory sliding-window rate limiter.
+#[derive(Debug)]
+pub struct RateLimiter {
+    windows: Mutex<HashMap<String, Vec<i64>>>,
+}
+
+impl RateLimiter {
+    pub fn new() -> Self {
+        RateLimiter {
+            windows: Mutex::new(HashMap::new()),
+        }
+    }
+
+    pub fn check_rate_limit(
+        &self,
+        client_id: &str,
+        max_requests: u32,
+        window_secs: u64,
+    ) -> anyhow::Result<bool> {
+        let now = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .unwrap_or_default()
+            .as_secs() as i64;
+
+        let cutoff = now.saturating_sub(window_secs as i64);
+        let mut windows = self.windows.lock().map_err(|e| {
+            anyhow::anyhow!("rate limiter lock poisoned: {e}")
+        })?;
+
+        let timestamps = windows.entry(client_id.to_string()).or_insert_with(Vec::new);
+        timestamps.retain(|&ts| ts >= cutoff);
+
+        if timestamps.len() >= max_requests as usize {
+            return Ok(false);
+        }
+
+        timestamps.push(now);
+        Ok(true)
+    }
+
+    pub fn reset(&self) -> anyhow::Result<()> {
+        let mut windows = self
+            .windows
+            .lock()
+            .map_err(|e| anyhow::anyhow!("rate limiter lock poisoned: {e}"))?;
+        windows.clear();
+        Ok(())
+    }
+}
+
+impl Default for RateLimiter {
+    fn default() -> Self {
+        Self::new()
+    }
+}