[enh] theme/simple: custom router

Lay the foundation for loading scripts granularly depending on the endpoint it's
on.

Remove vendor specific prefixes as there are now managed by browserslist and
LightningCSS.

Enabled quite a few rules in Biome that don't come in recommended to better
catch issues and improve consistency.

Related:

- https://github.com/searxng/searxng/pull/5073#discussion_r2256037965
- https://github.com/searxng/searxng/pull/5073#discussion_r2256057100

client/simple/package.json

@@ -25,27 +25,27 @@
     "not dead"
   ],
   "dependencies": {
-    "ionicons": "~8.0.13",
+    "ionicons": "~8.0.0",
     "normalize.css": "8.0.1",
-    "ol": "~10.6.1",
+    "ol": "~10.6.0",
     "swiped-events": "1.2.0"
   },
   "devDependencies": {
-    "@biomejs/biome": "2.1.2",
-    "@types/node": "~24.0.15",
-    "browserslist": "~4.25.1",
-    "browserslist-to-esbuild": "~2.1.1",
-    "edge.js": "~6.2.1",
+    "@biomejs/biome": "2.1.3",
+    "@types/node": "~24.2.0",
+    "browserslist": "~4.25.0",
+    "browserslist-to-esbuild": "~2.1.0",
+    "edge.js": "~6.2.0",
     "less": "~4.4.0",
-    "lightningcss": "~1.30.1",
-    "sharp": "~0.34.3",
+    "lightningcss": "~1.30.0",
+    "sharp": "~0.34.0",
     "sort-package-json": "~3.4.0",
-    "stylelint": "~16.22.0",
-    "stylelint-config-standard-less": "~3.0.1",
-    "stylelint-prettier": "~5.0.3",
+    "stylelint": "~16.23.0",
+    "stylelint-config-standard-less": "~3.0.0",
+    "stylelint-prettier": "~5.0.0",
     "svgo": "~4.0.0",
-    "typescript": "~5.8.3",
-    "vite": "npm:rolldown-vite@~7.0.9",
+    "typescript": "~5.9.0",
+    "vite": "npm:rolldown-vite@7.0.12",
     "vite-bundle-analyzer": "~1.1.0"
   }
 }