T07b: frontend feature pages — companies + contacts + settings + audit + dashboard + search

- 11 new feature pages (CompaniesList/Detail/Form, ContactsList/Detail/Form,
  SettingsProfile/Roles/Users, AuditLog, GlobalSearchResults)
- 3 page updates (Dashboard with StatCard+ActivityFeed, Settings with tree nav+Outlet,
  TopBar with SearchDropdown)
- 13 new routes in routes/index.tsx
- i18n updates (de.json + en.json) with companies/contacts/settings/audit/search keys
- 12 new test files + 2 existing test fixes (TopBar, AppShell)
- 7 shared components (DataGrid, Tabs, SearchDropdown, CsvImportDialog, StatCard,
  ActivityFeed, UnsavedChangesGuard)
- 16 new API hooks in hooks.ts
- Verification: 141 tests pass, build succeeds, tsc --noEmit clean

frontend/package-lock.json

@@ -10,6 +10,7 @@
       "dependencies": {
         "@hookform/resolvers": "^3.9.0",
         "@tanstack/react-query": "^5.56.0",
+        "@tanstack/react-table": "^8.21.3",
         "axios": "^1.7.7",
         "clsx": "^2.1.1",
         "i18next": "^23.14.0",
@@ -1332,6 +1333,37 @@
         "react": "^18 || ^19"
       }
     },
+    "node_modules/@tanstack/react-table": {
+      "version": "8.21.3",
+      "resolved": "https://registry.npmjs.org/@tanstack/react-table/-/react-table-8.21.3.tgz",
+      "integrity": "sha512-5nNMTSETP4ykGegmVkhjcS8tTLW6Vl4axfEGQN3v0zdHYbK4UfoqfPChclTrJ4EoK9QynqAu9oUf8VEmrpZ5Ww==",
+      "dependencies": {
+        "@tanstack/table-core": "8.21.3"
+      },
+      "engines": {
+        "node": ">=12"
+      },
+      "funding": {
+        "type": "github",
+        "url": "https://github.com/sponsors/tannerlinsley"
+      },
+      "peerDependencies": {
+        "react": ">=16.8",
+        "react-dom": ">=16.8"
+      }
+    },
+    "node_modules/@tanstack/table-core": {
+      "version": "8.21.3",
+      "resolved": "https://registry.npmjs.org/@tanstack/table-core/-/table-core-8.21.3.tgz",
+      "integrity": "sha512-ldZXEhOBb8Is7xLs01fR3YEc3DERiz5silj8tnGkFZytt1abEvl/GhUmCE0PMLaMPTa3Jk4HbKmRlHmu+gCftg==",
+      "engines": {
+        "node": ">=12"
+      },
+      "funding": {
+        "type": "github",
+        "url": "https://github.com/sponsors/tannerlinsley"
+      }
+    },
     "node_modules/@testing-library/dom": {
       "version": "10.4.1",
       "resolved": "https://registry.npmjs.org/@testing-library/dom/-/dom-10.4.1.tgz",