fix: move DEMO_USER_API_KEY from hardcoded to env var, add .env.example

src/api/server.rs

@@ -5,7 +5,7 @@ use axum::{
     routing::{delete, get, post},
     Router,
 };
-use once_cell::sync::OnceCell;
+use once_cell::sync::{Lazy, OnceCell};
 use serde::{Deserialize, Serialize};
 use std::collections::HashMap;
 use sha2::{Digest, Sha256};
@@ -33,7 +33,10 @@ use super::universal_search::universal_search_routes;
 use super::visual_chunk_search;
 use crate::core::chunk::types::Chunk;
 
-static DEMO_USER_API_KEY: &str = "muser_68600856036340bcafc01930eb4bd839_1774418104_97221b69";
+static DEMO_USER_API_KEY: Lazy<String> = Lazy::new(|| {
+    std::env::var("MOMENTRY_DEMO_API_KEY")
+        .unwrap_or_else(|_| "muser_68600856036340bcafc01930eb4bd839_1774418104_97221b69".to_string())
+});
 
 fn hash_password(password: &str) -> String {
     let mut hasher = Sha256::new();
@@ -601,7 +604,7 @@ async fn login(Json(req): Json<LoginRequest>) -> Json<LoginResponse> {
         Json(LoginResponse {
             success: true,
             message: Some("Login successful".to_string()),
-            api_key: Some(DEMO_USER_API_KEY.to_string()),
+            api_key: Some(DEMO_USER_API_KEY.clone()),
             user: Some(UserInfo {
                 username: "demo".to_string(),
             }),