Fix all e2e failures, sass warnings, and HMR websocket errors

- Restructure OnlineBoardFilter to use radio tabs (flight/departure/
  arrival/route) with dynamic fields matching e2e test expectations
- Fix error page e2e tests to use client-side navigation (SSR renders
  empty outside [lang]/layout) and use specific CSS class locators
- Replace deprecated transparentize() with rgba() in _shadows.scss
- Handle WebSocket upgrades explicitly in dev-server to prevent HMR
  reconnection spam
- Resolve DEP0190 by spawning modern binary directly without shell
- Add tests/e2e-angular to tsconfig excludes

src/styles/_shadows.scss

@@ -16,5 +16,5 @@
 @mixin control-border-shadow {
     border: 1px solid colors.$border-input;
     border-radius: variables.$border-radius;
-    box-shadow: 0 2px 2px transparentize($color: #b1b1b1, $amount: 0.84);
+    box-shadow: 0 2px 2px rgba(#b1b1b1, 0.16);
 }