Stable server fn endpoints: open tabs survive deploys

The 'previous question's resources until refresh' mystery: leptos's
auto-generated server fn routes embed a hash that changes across
builds. Every deploy therefore breaks every already-open tab - its
wasm keeps calling /api/get_question<oldhash>, the new server answers
400 'Could not find a server function at the route', and client-side
navigation quietly leaves the previous question's data on screen.
Refresh loads the new wasm with matching hashes, which is why it
always fixed it. Confirmed live: a pre-deploy client 400ed on
get_question2970801986613442004 while the freshly served wasm calls
get_question13103328088426240960, same source on both builds.

Explicit endpoint names decouple the URL from the build. This deploy
is the last breaking one; after it, old clients keep working.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/auth.rs

@@ -19,7 +19,7 @@ pub struct User {
 pub const SESSION_USER_KEY: &str = "user";
 
 /// Returns the currently signed-in user, if any.
-#[server]
+#[server(endpoint = "current_user")]
 pub async fn current_user() -> Result<Option<User>, ServerFnError> {
     let session: tower_sessions::Session = leptos_axum::extract().await?;
     let user = session