fix: switch API routing to query string for Nginx compatibility

public/index.php

@@ -64,11 +64,11 @@ $router->addRoute('GET', '/api/v1/health', function($request) {
     ]);
 });
 
-// ══ SPA Shell ═══════════════════════════════════════════════
-$fullPath = parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH);
+// ══ Determine if this is an API request ═════════════════════════════
+$apiRoute = $_GET['route'] ?? null;
 
-// Check if this is an API request (works regardless of subdirectory)
-if (!str_contains($fullPath, '/api/v1/')) {
+if (!$apiRoute) {
+    // Not an API call — serve the SPA shell
     include __DIR__ . '/shell.php';
     exit;
 }