Admin console: show the signed-in operator's name, not "Administrator"

The user switcher fell back to "Administrator" whenever /admin/api/status
returned no currentUser. Fresh sign-ins already embed the verified Emby
account name in the session cookie, but a session minted before that field
existed (or one that has not been re-issued since) is valid yet anonymous,
so the fallback showed for ever.

handleAdminConsole now treats a valid-but-anonymous admin session as needing
a fresh sign-in for the SPA shell only — a one-time prompt that fills the
name in, since session renewal preserves whatever the cookie already held.
Asset requests are unaffected, so nothing breaks mid-session.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011wS9Qz3Fkxeu9KPt26hhhx

server/internal/api/admin_spa.go

@@ -109,6 +109,14 @@ func (s *Server) handleAdminConsole(w http.ResponseWriter, r *http.Request) {
 		s.renderAccessLogin(w, r, "", http.StatusOK, r.URL.Path)
 		return
 	}
+	// A valid but anonymous session (minted before the cookie carried the operator's
+	// name) leaves the console unable to say who is signed in. Prompt for the shell only,
+	// so a fresh sign-in fills the name in without breaking asset requests mid-session.
+	if isAdminDocumentRequest(r) && !s.adminSessionNamed(r) {
+		s.renderAccessLogin(w, r, "Please sign in again to continue.",
+			http.StatusOK, r.URL.Path)
+		return
+	}
 	// Opening a page is somebody at the keyboard, so it starts the clock again.
 	s.renewAdminSession(w, r)
 	s.setAdminTokenCookie(w, r)