fix(tenancy): fix table column alignment with flattened row approach

The nested tbody approach caused browsers to collapse all cells into
one column. Replaced with a single flat x-for loop over flattenedRows
(computed property that interleaves member rows and store sub-rows).

Each row is a single <tr> with 4 proper <td> cells, using x-if to
conditionally render member-level or store-level content per column.
Sub-rows are hidden/shown via expandedMembers array.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/modules/tenancy/static/merchant/js/merchant-team.js

@@ -131,6 +131,21 @@ function merchantTeam() {
             );
         },
 
+        /**
+         * Flatten members + their stores into a single row list for table rendering.
+         * Each row is either {type:'member', member, key} or {type:'store', member, store, key}
+         */
+        get flattenedRows() {
+            const rows = [];
+            for (const member of this.filteredMembers) {
+                rows.push({ type: 'member', member, key: `m-${member.user_id}` });
+                for (const store of member.stores) {
+                    rows.push({ type: 'store', member, store, key: `s-${member.user_id}-${store.store_id}` });
+                }
+            }
+            return rows;
+        },
+
         /**
          * Toggle expand/collapse for a member's store rows
          */