Fix: Preserve ?v= parameter when auto-redirecting to For You feed

When a user visits a direct video link (e.g. `/?v=...`) while logged in,
the application auto-authenticates and redirects the view to `#view=for-you`.
Previously, `setHashView` unconditionally removed all query parameters, causing
the video modal to fail to open because the `v` parameter was lost before it could be read.

This change:
1.  Updates `setHashView` to accept an options object, allowing specific parameters to be preserved.
2.  Updates `handleAuthLogin` in `app.js` to detect if a `v` parameter is present and request its preservation during the view switch.

js/hashView.js

@@ -14,14 +14,16 @@ export function getHashViewName() {
   return viewName.trim();
 }
 
-export function setHashView(viewName) {
+export function setHashView(viewName, options = {}) {
   if (typeof window === "undefined") {
     return;
   }
 
   const url = new URL(window.location.href);
   url.searchParams.delete("modal");
-  url.searchParams.delete("v");
+  if (!options?.preserveVideoParam) {
+    url.searchParams.delete("v");
+  }
   const newUrl = url.pathname + url.search + `#view=${viewName}`;
   window.history.replaceState({}, "", newUrl);