v15.3.1-canary.4

Core Changes

• fix: ensure app router not found works when deployed with pages i18n config: #77905
• Uninstall existing uncaughtException listeners to prevent the process from crashing: #78042

Misc Changes

• Update Rust toolchain to nightly-2025-04-10: #78039

Credits

Huge thanks to @wbinnssmith, @ztanner, and @acdlite for helping!