Move login JS to a separate file

Mostly so the base URL resolution code can be shared.

src/browser/pages/login.html

@@ -47,10 +47,5 @@
     </div>
   </body>
   <script data-cfasync="false" src="{{CS_STATIC_BASE}}/dist/register.js"></script>
-  <script>
-    const parts = window.location.pathname.replace(/^\//g, "").split("/")
-    parts[parts.length - 1] = "{{BASE}}"
-    const url = new URL(window.location.origin + "/" + parts.join("/"))
-    document.getElementById("base").value = url.pathname
-  </script>
+  <script data-cfasync="false" src="{{CS_STATIC_BASE}}/dist/login.js"></script>
 </html>

src/browser/pages/login.ts

@@ -0,0 +1,7 @@
+import { getOptions } from "../../common/util"
+
+const options = getOptions()
+const el = document.getElementById("base") as HTMLInputElement
+if (el) {
+  el.value = options.base
+}