fix: cell-network name, install error surfacing, health history cleanup

- docker-compose.services.yml: change external network name from
  pic_cell-network to cell-network so store-service compose files can find
  it.  The project-prefixed name was overriding the explicit name: cell-network
  fix in docker-compose.yml when both files were merged by make start.

- service_store.py: normalize docker compose stderr into the error key in
  the 400 response so the Store page shows the actual failure reason instead
  of the generic fallback message.

- app.py: skip health checks for email/calendar/files managers when those
  optional store services are not installed — prevents false Down alerts and
  unnecessary noise in health history.

- Logs.jsx: remove Email/Calendar/Files columns from the health history table;
  they are optional store services, not core builtins that should always appear.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

webui/src/pages/Logs.jsx

@@ -392,7 +392,7 @@ function HealthHistoryTab() {
           <table className="min-w-full text-sm">
             <thead>
               <tr className="bg-gray-100">
-                {['Timestamp','Network','WireGuard','Email','Calendar','Files','Routing','Vault','Alerts'].map(h => (
+                {['Timestamp','Network','WireGuard','Routing','Vault','Alerts'].map(h => (
                   <th key={h} className="px-2 py-1 text-left">{h}</th>
                 ))}
               </tr>
@@ -403,9 +403,6 @@ function HealthHistoryTab() {
                   <td className="px-2 py-1 font-mono text-xs">{h.timestamp}</td>
                   <td className="px-2 py-1"><SvcCol data={h.network} /></td>
                   <td className="px-2 py-1"><SvcCol data={h.wireguard} /></td>
-                  <td className="px-2 py-1"><SvcCol data={h.email} /></td>
-                  <td className="px-2 py-1"><SvcCol data={h.calendar} /></td>
-                  <td className="px-2 py-1"><SvcCol data={h.files} /></td>
                   <td className="px-2 py-1"><SvcCol data={h.routing} /></td>
                   <td className="px-2 py-1"><SvcCol data={h.vault} /></td>
                   <td className="px-2 py-1">