feat(admin-settings): radio field type + adopt for Documenso signing-order + send-mode

Adds a 'radio' SettingType the registry-driven admin form can render. Same
shape as 'select' (options list, enum validation, resolved/source badges),
but renders inline radio cards instead of a dropdown so each option's
consequences sit side-by-side for the admin.

Adopted on the two highest-stakes Documenso behaviour toggles:
- `eoi_send_mode` — Manual vs Auto signing-invitation dispatch
- `documenso_signing_order` — Parallel vs Sequential recipient flow

Both choices are binary and materially different (one auto-sends mail, the
other doesn't; one routes signing serially, the other in parallel), so the
upfront comparison beats a hidden dropdown.

`documenso_redirect_url` keeps its url-input — it's already a single
free-text field with no enum.

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

src/components/admin/shared/registry-driven-form.tsx

@@ -28,6 +28,7 @@ type SettingType =
   | 'number'
   | 'boolean'
   | 'select'
+  | 'radio'
   | 'url'
   | 'email'
   | 'textarea'
@@ -526,6 +527,36 @@ function FieldInput({
       />
     );
   }
+  if (entry.type === 'radio' && entry.options) {
+    // Inline radio group — clearer than a dropdown for 2–3 mutually-exclusive
+    // options where each choice has materially different consequences (e.g.
+    // auto-vs-manual signing dispatch). Falls through to plain Select when
+    // the option count grows.
+    const current = value == null ? null : String(value);
+    return (
+      <div role="radiogroup" aria-labelledby={`${entry.key}-label`} className="space-y-2">
+        {entry.options.map((o) => {
+          const checked = current === o.value;
+          return (
+            <label
+              key={o.value}
+              className="flex cursor-pointer items-start gap-2 rounded-md border border-input bg-background p-2 text-sm hover:bg-accent/40 has-[:checked]:border-primary has-[:checked]:bg-accent/60"
+            >
+              <input
+                type="radio"
+                name={entry.key}
+                value={o.value}
+                checked={checked}
+                onChange={() => onChange(o.value)}
+                className="mt-1 h-4 w-4 cursor-pointer accent-primary"
+              />
+              <span className="flex-1">{o.label}</span>
+            </label>
+          );
+        })}
+      </div>
+    );
+  }
   if (entry.type === 'select' && entry.options) {
     // Radix Select rejects an empty-string `value` because that's its internal
     // sentinel for "cleared". Pass `undefined` instead so the placeholder