Add Knip unused-code checks

package.json

@@ -18,6 +18,7 @@
     "start": "HOST=127.0.0.1 node .output/server/index.mjs",
     "typecheck": "tsc --noEmit",
     "lint": "biome check .",
+    "knip": "knip",
     "format": "biome check --write .",
     "test": "vitest run",
     "test:watch": "vitest",
@@ -38,7 +39,6 @@
   "devDependencies": {
     "@biomejs/biome": "2.5.3",
     "@playwright/test": "1.61.1",
-    "@tanstack/router-cli": "1.167.18",
     "@testing-library/dom": "10.4.1",
     "@testing-library/jest-dom": "6.9.1",
     "@testing-library/react": "16.3.2",
@@ -47,6 +47,7 @@
     "@types/react-dom": "19.2.3",
     "@vitejs/plugin-react": "6.0.3",
     "jsdom": "29.1.1",
+    "knip": "6.27.0",
     "typescript": "7.0.2",
     "vite": "8.1.4",
     "vitest": "4.1.10"