Implement simple persistent cache with automatic saving on status changes

shared/src/cache.rs

@@ -3,23 +3,13 @@ use serde::{Deserialize, Serialize};
 /// Cache configuration
 #[derive(Debug, Clone, Deserialize, Serialize)]
 pub struct CacheConfig {
-    pub enabled: bool,
-    pub default_ttl_seconds: u64,
-    pub max_entries: usize,
-    pub warming_timeout_seconds: u64,
-    pub background_refresh_enabled: bool,
-    pub cleanup_interval_seconds: u64,
+    pub persist_path: String,
 }
 
 impl Default for CacheConfig {
     fn default() -> Self {
         Self {
-            enabled: true,
-            default_ttl_seconds: 30,
-            max_entries: 10000,
-            warming_timeout_seconds: 3,
-            background_refresh_enabled: true,
-            cleanup_interval_seconds: 1800,
+            persist_path: "/var/lib/cm-dashboard/cache.json".to_string(),
         }
     }
 }