fix(api): security hardening — helmet + auth rate limiting (#641)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

pnpm-lock.yaml

@@ -180,6 +180,9 @@ importers:
       gray-matter:
         specifier: ^4.0.3
         version: 4.0.3
+      helmet:
+        specifier: ^8.1.0
+        version: 8.1.0
       highlight.js:
         specifier: ^11.11.1
         version: 11.11.1
@@ -5210,6 +5213,10 @@ packages:
     resolution: {integrity: sha512-0hJU9SCPvmMzIBdZFqNPXWa6dqh7WdH0cII9y+CyS8rG3nL48Bclra9HmKhVVUHyPWNH5Y7xDwAB7bfgSjkUMQ==}
     engines: {node: '>= 0.4'}
 
+  helmet@8.1.0:
+    resolution: {integrity: sha512-jOiHyAZsmnr8LqoPGmCjYAaiuWwjAPLgY8ZX2XrmHawt99/u1y6RgrZMTeoPfpUbV96HOalYgz1qzkRbw54Pmg==}
+    engines: {node: '>=18.0.0'}
+
   highlight.js@11.11.1:
     resolution: {integrity: sha512-Xwwo44whKBVCYoliBQwaPvtd/2tYFkRQtXDWj1nackaV2JPXx3L0+Jvd8/qCJ2p+ML0/XVkJ2q+Mr+UVdpJK5w==}
     engines: {node: '>=12.0.0'}
@@ -12815,6 +12822,8 @@ snapshots:
     dependencies:
       function-bind: 1.1.2
 
+  helmet@8.1.0: {}
+
   highlight.js@11.11.1: {}
 
   html-encoding-sniffer@4.0.0: