feat(hephaestus.x): landing 'Sign in' becomes a Bitcoin Cash wallet dropdown

- site/hephaestus.x/index.html: replace single 'Sign in with wallet' CTA with
  a <details> dropdown labelled 'Bitcoin Cash wallet'. Menu items:
    Sign in       -> /user/oauth2/hephaestus-wallet#import
    Sign up       -> /user/oauth2/hephaestus-wallet#create   (pill: easiest)
    WizardConnect -> /user/oauth2/hephaestus-wallet#connect  (pill: most private)
  Same emoji + copy scheme as the wallet accordion, so the landing previews
  the choices the user will see after clicking through.

- Hephaestus/auth-proxy/public/wallet.js: renderTabs() now reads location.hash
  and auto-opens the matching <details> option on load (create/import/connect).
  Fragments survive Forgejo's OAuth redirect chain, so a click on 'Sign up'
  from the landing lands the user directly on the Create accordion.

auth-proxy/public/wallet.js

@@ -211,6 +211,14 @@ function renderTabs() {
       }
     });
   });
+
+  // Auto-open a specific option when the URL fragment is one of #create / #import / #connect
+  // (e.g. links from the hephaestus.x landing dropdown). Fragments survive OAuth redirects.
+  const hash = (location.hash || "").replace(/^#/, "").toLowerCase();
+  if (hash === "create" || hash === "import" || hash === "connect") {
+    const target = app.querySelector(`details.wallet-opt[data-choice="${hash}"]`);
+    if (target) target.open = true;
+  }
 }
 
 function populateFlow(kind, flow) {