feat(server): persist activity history on the server and expose it to the dashboard UI via /api/activity instead of relying on fragile localStorage

server/src/state.rs

@@ -27,6 +27,7 @@ pub struct MemoryState {
     pub tech_debts: Store<Vec<TechDebt>>,
     pub gates: Store<Vec<GateRecord>>,
     pub context_workspaces: Store<Vec<ContextWorkspace>>,
+    pub recent_activities: Store<std::collections::VecDeque<serde_json::Value>>,
     pub activity_tx: tokio::sync::broadcast::Sender<String>,
 }
 
@@ -37,9 +38,26 @@ impl MemoryState {
     }
 
     pub fn broadcast_activity(&self, message: &str) {
+        let time = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .unwrap_or_default()
+            .as_millis() as u64;
+            
+        let item = serde_json::json!({
+            "time": time,
+            "message": message
+        });
+        
+        self.recent_activities.modify(|activities| {
+            activities.push_back(item.clone());
+            if activities.len() > 100 {
+                activities.pop_front();
+            }
+        });
+
         let payload = serde_json::json!({
             "type": "activity",
-            "data": message
+            "data": item
         })
         .to_string();
         let _ = self.activity_tx.send(payload);