Make API URL dynamic based on hostname

- localhost/127.0.0.1 → http://localhost:8000/api/v1
- Local network IPs → http://{hostname}:8000/api/v1
- Production domains → https://{hostname}/api/v1 (requires reverse proxy)

frontend/src/lib/api.ts

@@ -1,20 +1,44 @@
 /**
  * API client for pounce backend
+ * 
+ * API URL is determined dynamically based on the current hostname:
+ * - localhost/127.0.0.1 → http://localhost:8000/api/v1
+ * - Local network IPs (10.x, 192.168.x) → http://{hostname}:8000/api/v1
+ * - Production (any other domain) → https://{hostname}/api/v1 (requires reverse proxy)
  */
 
-// Ensure API_BASE ends with /api/v1 and no trailing slash
-const getApiBase = () => {
-  const baseUrl = process.env.NEXT_PUBLIC_API_URL || 'http://localhost:8000'
-  // Remove trailing slash if present
-  const cleanBase = baseUrl.replace(/\/$/, '')
-  // Add /api/v1 if not present
-  if (cleanBase.endsWith('/api/v1')) {
-    return cleanBase
-  }
-  return `${cleanBase}/api/v1`
+const getApiBase = (): string => {
+  // Server-side rendering: use environment variable or localhost
+  if (typeof window === 'undefined') {
+    const baseUrl = process.env.NEXT_PUBLIC_API_URL || 'http://localhost:8000/api/v1'
+    return baseUrl.replace(/\/$/, '')
   }
 
-const API_BASE = getApiBase()
+  const { protocol, hostname, port } = window.location
+
+  // Localhost development
+  if (hostname === 'localhost' || hostname === '127.0.0.1') {
+    return 'http://localhost:8000/api/v1'
+  }
+
+  // Local network (10.x.x.x, 192.168.x.x, 172.16-31.x.x)
+  if (/^(10\.|192\.168\.|172\.(1[6-9]|2[0-9]|3[01])\.)/.test(hostname)) {
+    return `http://${hostname}:8000/api/v1`
+  }
+
+  // Production: use same protocol and domain with /api/v1 path
+  // This requires a reverse proxy (nginx/caddy) to route /api/v1 to the backend
+  return `${protocol}//${hostname}/api/v1`
+}
+
+// Lazy-evaluated to ensure window is available on client
+let _apiBase: string | null = null
+const getApiBaseUrl = (): string => {
+  if (_apiBase === null) {
+    _apiBase = getApiBase()
+  }
+  return _apiBase
+}
 
 interface ApiError {
   detail: string
@@ -44,7 +68,7 @@ class ApiClient {
     endpoint: string,
     options: RequestInit = {}
   ): Promise<T> {
-    const url = `${API_BASE}${endpoint}`
+    const url = `${getApiBaseUrl()}${endpoint}`
     const headers: Record<string, string> = {
       'Content-Type': 'application/json',
       ...options.headers as Record<string, string>,