Fix LAN API base and development CORS regression

frontend/src/lib/api.ts

@@ -14,9 +14,25 @@ import type {
 } from '../types';
 
 /**
- * Resolves backend base URL from environment with localhost fallback.
+ * Resolves backend base URL from environment with current-host HTTP fallback.
  */
-const API_BASE = import.meta.env?.VITE_API_BASE ?? 'http://localhost:8000/api/v1';
+function resolveApiBase(): string {
+  const envValue = import.meta.env?.VITE_API_BASE;
+  if (typeof envValue === 'string') {
+    const trimmed = envValue.trim().replace(/\/+$/, '');
+    if (trimmed) {
+      return trimmed;
+    }
+  }
+
+  if (typeof window !== 'undefined' && window.location?.hostname) {
+    return `http://${window.location.hostname}:8000/api/v1`;
+  }
+
+  return 'http://localhost:8000/api/v1';
+}
+
+const API_BASE = resolveApiBase();
 
 /**
  * Legacy environment token fallback used only when no runtime token source is available.