fix(viewer): minimalist login page — brand + button, drop redundant copy

The "Sign in" heading + "Choose a sign-in method to continue." subtitle
were committee copy: the brand header identifies the app, the button
already labels the action. Removed both visible elements; kept an
``sr-only`` h1 ("Sign in to Equalify Reflow") so the page still has a
heading landmark for screen-reader navigation.

Same simplification applied to basic mode (the form labels + submit
button text already communicate everything the heading was repeating).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: bbertucc

clients/viewer/src/auth/LoginPage.tsx

@@ -71,12 +71,7 @@ export function LoginPage() {
       <main className="flex min-h-screen items-center justify-center bg-background px-4">
         <section className="w-full max-w-sm space-y-6 rounded-lg border border-border bg-card p-8 shadow-lg">
           <BrandHeader />
-          <header>
-            <h1 className="text-2xl font-bold">Sign in</h1>
-            <p className="mt-1 text-sm text-muted-foreground">
-              Choose a sign-in method to continue.
-            </p>
-          </header>
+          <h1 className="sr-only">Sign in to Equalify Reflow</h1>
           <ul className="space-y-3">
             {config.providers.map((provider) => {
               const url = new URL(provider.login_url, window.location.origin)
@@ -105,12 +100,7 @@ export function LoginPage() {
     <main className="flex min-h-screen items-center justify-center bg-background px-4">
       <section className="w-full max-w-sm space-y-6 rounded-lg border border-border bg-card p-8 shadow-lg">
         <BrandHeader />
-        <header>
-          <h1 className="text-2xl font-bold">Sign in</h1>
-          <p className="mt-1 text-sm text-muted-foreground">
-            Enter your username and password to continue.
-          </p>
-        </header>
+        <h1 className="sr-only">Sign in to Equalify Reflow</h1>
         <form className="space-y-4" onSubmit={handleSubmit} noValidate>
           <label className="block space-y-1">
             <span className="text-sm font-medium">Username</span>