chore: pin Tailwind 4.3.1, which drops module.register() (closes #355)

@tailwindcss/node 4.2.1, loaded by the Tailwind CLI, calls Node's
deprecated module.register() as it starts, so every make build on a
current Node printed the DEP0205 warning. 4.3.1 is the first release that
calls module.registerHooks() instead wherever Node has it.

tailwindcss and @tailwindcss/cli are pinned at exactly 4.3.1, and
yarn.lock carries the new versions of the packages they pull in. The
compiled CSS computes to the same values: it drops the unused .start and
.end rules and writes calc(var(--spacing) * 1) as var(--spacing).

Model: opus-5-5

package.json

@@ -15,14 +15,14 @@
     },
     "devDependencies": {
         "@eslint/js": "10.0.1",
-        "@tailwindcss/cli": "^4.2.1",
+        "@tailwindcss/cli": "4.3.1",
         "esbuild": "^0.27.3",
         "eslint": "10.8.1",
         "globals": "17.11.0",
         "jest": "^30.2.0",
         "playwright-core": "1.56.0",
         "prettier": "^3.8.1",
-        "tailwindcss": "^4.2.1"
+        "tailwindcss": "4.3.1"
     },
     "dependencies": {
         "ethereum-blockies-base64": "^1.0.2",