fix: call fetchMe after token acquire regardless of loading state

loading starts as true in the store, so the previous condition
`!user && !loading` prevented fetchMe from ever being called after
the Azure AD redirect — causing a permanent Loading spinner.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/App.tsx

@@ -38,7 +38,7 @@ function AuthGate({ children }: { children: React.ReactNode }) {
           scopes: ['openid', 'profile', 'email'],
         })
         setToken(result.idToken)
-        if (!user && !loading) fetchMe()
+        if (!user) fetchMe()
       } catch {
         instance.loginRedirect({ scopes: ['openid', 'profile', 'email'] })
       }