Non-ASCII characters in the slug may cause navigation and routing to break

### Link to the code that reproduces this issue https://github.com/joulev/debug/tree/nextjs-with-non-ascii-chars ### To Reproduce Simply start the application in either dev mode or prod mode or on Vercel. Vercel prod mode deployment of the reproduction repo above is already available on https://debug-git-nextjs-with-non-ascii-chars-joulev-proj.vercel.app. ### Current vs. Expected behavior **Current behaviour** | | Server `redirect` | Client `router.push` | `next/link` | |---|---|---|---| | Local `next dev` | ❌ Error | ❌ 404 | ❌ 404 | | Local `next start` | ❌ Error | ❌ 404 | ❌ 404 | | Vercel | ❌ Error | ✅ | ✅ | **Expected behaviour:** All 9 cases above should work. ### Provide environment information ```bash Operating System: Platform: darwin Arch: arm64 Version: Darwin Kernel Version 24.2.0: Fri Dec 6 18:51:28 PST 2024; root:xnu-11215.61.5~2/RELEASE_ARM64_T8112 Available memory (MB): 16384 Available CPU cores: 8 Binaries: Node: 22.12.0 npm: 10.9.0 Yarn: N/A pnpm: 9.15.0 Relevant Packages: next: 15.1.0 // Latest available version is detected (15.1.0). eslint-config-next: N/A react: 19.0.0 react-dom: 19.0.0 typescript: 5.7.2 Next.js Config: output: N/A ``` ### Which area(s) are affected? (Select all that apply) Navigation ### Which stage(s) are affected? (Select all that apply) next dev (local), next start (local), Vercel (Deployed) ### Additional context _No response_