feat: add statistics API and dashboard for asset metrics

- Implemented `/api/stats` endpoint to return JSON metrics including active assets, total uploads, storage usage, and recent activity.
- Created `stats.html` page to display real-time statistics with auto-refresh functionality.
- Enhanced asset logging to include uploader IP and detailed event information for uploads and deletions.
- Updated asset model to store uploader IP for audit purposes.
- Improved logging functionality to ensure log directory exists before writing.
- Refactored asset creation and management to support new features and logging.

src/data_mgt.rs

@@ -3,6 +3,7 @@ use chrono::{Duration, Utc};
 use serde::{Deserialize, Serialize};
 
 use crate::DATA_STORAGE;
+use crate::logs::log_asset_event;
 
 #[derive(Debug, Serialize, Deserialize, Default)]
 pub struct Asset {
@@ -12,10 +13,12 @@ pub struct Asset {
     expires_at: i64,
     mime: String,
     content: Vec<u8>,
+    #[serde(default)]
+    uploader_ip: Option<String>,
 }
 
 impl Asset {
-    pub fn new(share_duration: u32, mime: String, content: Vec<u8>) -> Self {
+    pub fn new(share_duration: u32, mime: String, content: Vec<u8>, uploader_ip: Option<String>) -> Self {
         let id = uuid::Uuid::new_v4().to_string();
         let created_at = Utc::now().timestamp_millis();
         let expires_at = created_at + Duration::minutes(share_duration as i64).num_milliseconds();
@@ -26,6 +29,7 @@ impl Asset {
             expires_at,
             mime,
             content,
+            uploader_ip,
         }
     }
     pub fn is_expired(&self) -> bool {
@@ -44,6 +48,26 @@ impl Asset {
         self.content.clone()
     }
 
+    pub fn share_duration(&self) -> u32 {
+        self.share_duration
+    }
+
+    pub fn created_at(&self) -> i64 {
+        self.created_at
+    }
+
+    pub fn expires_at(&self) -> i64 {
+        self.expires_at
+    }
+
+    pub fn size_bytes(&self) -> usize {
+        self.content.len()
+    }
+
+    pub fn uploader_ip(&self) -> Option<&str> {
+        self.uploader_ip.as_deref()
+    }
+
     pub fn to_bytes(&self) -> Result<Vec<u8>> {
         let bytes = serde_json::to_vec(self)?;
         Ok(bytes)
@@ -68,6 +92,16 @@ pub async fn clear_assets() -> Result<()> {
             let asset = serde_json::from_slice::<Asset>(&data)?;
             if asset.is_expired() {
                 println!("Removing expired asset: {}", asset.id());
+                log_asset_event(
+                    "delete_expired",
+                    asset.id(),
+                    asset.mime(),
+                    asset.size_bytes(),
+                    asset.share_duration(),
+                    asset.created_at(),
+                    asset.expires_at(),
+                    asset.uploader_ip().unwrap_or("-"),
+                );
                 std::fs::remove_file(&path)?;
             }
         }