remove preact and create setup wizard

apps/server/internal/httpserver/templates/setup.gohtml

@@ -0,0 +1,34 @@
+{{ define "setup.gohtml" }}{{ template "base" . }}{{ end }}
+
+{{ define "setup_content" }}
+<section class="auth-shell">
+  <div class="auth-panel">
+    <div class="auth-panel__header">
+      <p class="eyebrow">Cairnquire</p>
+      <h1>Initial setup</h1>
+      <p class="auth-note">Create the first administrator account and choose whether visitors can register their own accounts.</p>
+    </div>
+
+    <form class="auth-form" data-initial-setup>
+      <label>
+        Admin email
+        <input type="email" name="email" autocomplete="email" required />
+      </label>
+      <label>
+        Display name
+        <input type="text" name="displayName" autocomplete="name" />
+      </label>
+      <label>
+        Password
+        <input type="password" name="password" autocomplete="new-password" minlength="12" required />
+      </label>
+      <label class="auth-choice">
+        <input type="checkbox" name="signupsEnabled" />
+        Allow visitors to create accounts
+      </label>
+      <button type="submit" class="btn-primary">Finish setup</button>
+      <p class="form-status" data-setup-status></p>
+    </form>
+  </div>
+</section>
+{{ end }}