feat(account): add email/password sign-up to account page

The sign-in form only offered social auth and a link to /checkout.
Users wanting to create an account directly had no path.

Changes:
- "No account? Create one" toggle replaces the old "Choose a plan" link
- switchToSignUp() / switchToSignIn() toggle button label, placeholder,
  and autocomplete between sign-in and sign-up modes
- Explicit signUpWithEmail() calls signUp() directly; with autoconfirm
  enabled it returns a session immediately and reloads into the dashboard
- signInWithEmail() simplified: no silent sign-up fallback, clean errors
- Re-extract account JS (6dafc1586705 -> dadeb8ddb9a8)
- Re-extract styles chat JS (de72b8b61d75 -> 02ecc8cf6542) as side effect
  of extract-js.py run

src/account.el

@@ -686,8 +686,8 @@ fn account_page(supabase_url: String, supabase_anon_key: String) -> String {
             style=\"font-family:var(--body);font-size:.75rem;font-weight:500;letter-spacing:.14em;text-transform:uppercase;color:#fff;background:var(--navy);border:none;padding:.875rem 1rem;cursor:pointer;transition:background .2s;width:100%;box-sizing:border-box\">
             Sign in
           </button>
-          <p style=\"font-family:var(--body);font-size:.8rem;font-weight:300;color:var(--t3);text-align:center\">
-            New here? <a href=\"/checkout\" style=\"color:var(--navy)\">Choose a plan to get started</a>
+          <p id=\"acct-mode-hint\" style=\"font-family:var(--body);font-size:.8rem;font-weight:300;color:var(--t3);text-align:center\">
+            No account? <a href=\"#\" onclick=\"switchToSignUp();return false;\" style=\"color:var(--navy)\">Create one</a>
           </p>
           <p id=\"acct-email-msg\" style=\"display:none;font-size:.8rem;text-align:center;margin-top:.25rem\"></p>
         </div>
@@ -896,7 +896,7 @@ fn account_page(supabase_url: String, supabase_anon_key: String) -> String {
 </div>
 
 <script src=\"https://cdn.jsdelivr.net/npm/@supabase/supabase-js@2/dist/umd/supabase.min.js\"></script>
-<script>window.NEURON_CFG=window.NEURON_CFG||{};window.NEURON_CFG.supabase_url=\"" + supabase_url + "\";window.NEURON_CFG.supabase_anon_key=\"" + supabase_anon_key + "\";</script><script src=\"/assets/js/6dafc1586705.js\" defer></script>
+<script>window.NEURON_CFG=window.NEURON_CFG||{};window.NEURON_CFG.supabase_url=\"" + supabase_url + "\";window.NEURON_CFG.supabase_anon_key=\"" + supabase_anon_key + "\";</script><script src=\"/assets/js/dadeb8ddb9a8.js\" defer></script>
 
 </body>
 </html>"