connectors: merge the catalog page into a row-list Connectors page

The standalone Catalog page added nothing the Connectors page could not
do: drop it (component, route, sidebar entry) and move its affordances
onto the Connectors page — the Add-connector dropdown (marketplace /
manual form, now at #connectors/new) and per-row removal for the admin.

Replace the card grid with a sharper row list (4px radius) built for
scanning status and acting; the marketplace's back link now returns to
#connectors. i18n keys renamed catalog.* -> connectors.add/new/*.

web/app.js

@@ -19,7 +19,6 @@ import { PluginPageHost }     from './components/plugin-page-host.js';
 import { PluginCatalogPage }  from './components/plugin-catalog.js';
 import { PluginDetailPage }   from './components/plugin-detail.js';
 import { MarketplacePage }    from './components/marketplace.js';
-import { CatalogPage }        from './components/catalog.js';
 import { ProfilePage }        from './components/profile-page.js';
 import { ApprovalGroupsPage } from './components/approval-groups.js';
 import { ApprovalRulesPage }  from './components/approval-rules.js';
@@ -62,7 +61,6 @@ customElements.define('plugin-page-host',     PluginPageHost);
 customElements.define('plugin-catalog-page',  PluginCatalogPage);
 customElements.define('plugin-detail-page',   PluginDetailPage);
 customElements.define('marketplace-page',     MarketplacePage);
-customElements.define('catalog-page',         CatalogPage);
 customElements.define('profile-page',         ProfilePage);
 customElements.define('approval-groups-page', ApprovalGroupsPage);
 customElements.define('approval-rules-page',  ApprovalRulesPage);