Remove contact identity fields from Stage 0 and widen Current stage

Drop the readonly First name, Last name, and Email fields from the
Check-in (organizing) section display. Add an optional fullWidth flag to
FieldConfig and set it on current_stage so it spans the full section grid.

components/StageSection.tsx

@@ -259,6 +259,7 @@ export function StageSection({
               {visibleFields.map((f) => {
                 const resolvedOptions = f.optionGroupId ? options[f.optionGroupId] : undefined;
                 const wide =
+                  f.fullWidth ||
                   f.type === "textarea" ||
                   f.type === "boolean" ||
                   f.type === "multiselect";
@@ -426,7 +427,10 @@ function FieldGroupCard({
         {fields.map((f) => {
           const resolvedOptions = f.optionGroupId ? options[f.optionGroupId] : undefined;
           const wide =
-            f.type === "textarea" || f.type === "boolean" || f.type === "multiselect";
+            f.fullWidth ||
+            f.type === "textarea" ||
+            f.type === "boolean" ||
+            f.type === "multiselect";
           return (
             <div key={f.name} className={wide ? "md:col-span-2" : ""}>
               <FieldRenderer