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/logs.rs

@@ -11,6 +11,12 @@ pub fn log_to_file(req: &HttpRequest, start: Instant) {
 
     let log_path = LOG_DIR.to_string() + "access.log";
 
+    // Ensure log directory exists
+    if let Err(e) = std::fs::create_dir_all(LOG_DIR) {
+        eprintln!("failed to create log dir: {}", e);
+        return;
+    }
+
     let Ok(mut file) = OpenOptions::new().create(true).append(true).open(log_path) else {
         eprintln!("failed to open log file");
         return;
@@ -40,3 +46,35 @@ pub fn log_to_file(req: &HttpRequest, start: Instant) {
 
     let _ = file.write_all(line.as_bytes());
 }
+
+pub fn log_asset_event(
+    action: &str,
+    id: &str,
+    mime: &str,
+    size_bytes: usize,
+    duration_min: u32,
+    created_at_ms: i64,
+    expires_at_ms: i64,
+    uploader_ip: &str,
+) {
+    // Ensure logging directory exists before writing
+    if let Err(e) = std::fs::create_dir_all(LOG_DIR) {
+        eprintln!("failed to create log dir for asset event: {}", e);
+        return;
+    }
+
+    let log_path = LOG_DIR.to_string() + "access.log";
+
+    let Ok(mut file) = OpenOptions::new().create(true).append(true).open(log_path) else {
+        eprintln!("failed to open log file for asset event");
+        return;
+    };
+
+    let ts = chrono::Local::now().to_rfc3339();
+
+    let line = format!(
+        "{ts} event=asset action={action} id={id} mime={mime} size_bytes={size_bytes} duration_min={duration_min} created_at_ms={created_at_ms} expires_at_ms={expires_at_ms} uploader_ip={uploader_ip}\n"
+    );
+
+    let _ = file.write_all(line.as_bytes());
+}