refactor(web): unify settings dialogs into single dialog with sidebar

Merge API integration, model settings, account settings and storage
analysis into one SettingsDialog with a shadcn inner sidebar for
section switching. Preserve existing ?action= query-param deep links
(showModelSettings / showAccountSettings / showApiIntegrationSettings /
showStorageAnalysis) by mapping each to a section. Extract reusable
panels and keep ModelsDialog as a thin wrapper for the dynamic-form
model picker.

web/src/i18n/locales/en-US.ts

@@ -1386,6 +1386,9 @@ const enUS = {
     boxSessionCreated: 'Created',
     boxSessionLastUsed: 'Last used',
   },
+  settingsDialog: {
+    title: 'Settings',
+  },
   storageAnalysis: {
     title: 'Storage Analysis',
     description: 'Inspect storage usage and cleanup candidates',