main: use dotenv to load .env

src/main.rs

@@ -587,7 +587,9 @@ async fn main() {
         println!("Panic: {}", msg);
     }));
 
-    if option_env!("OPENAI_API_KEY").is_none() {
+    dotenv::dotenv().ok();
+
+    if std::env::var("OPENAI_API_KEY").is_err() {
         eprintln!("Error: OPENAI_API_KEY environment variable not set. The application will not function without it.");
         return;
     }