chore: switch from eslint to oxlint

- Replace eslint and its plugins with oxlint, add .oxlintrc.json
- Add type-check and check scripts, drop deploy and predeploy
- Remove the GitHub Pages deploy workflow
- Move dayjs setup to src/lib and export the configured instance
- Bump React to 19.3, Vite to 8.3, Tailwind to 4.3 and other deps
- Reformat the contact page with prettier

.oxlintrc.json

@@ -0,0 +1,7 @@
+{
+  "plugins": ["react", "react-hooks", "typescript"],
+  "rules": {
+    "react-hooks/rules-of-hooks": "error",
+    "react-hooks/exhaustive-deps": "warn"
+  }
+}