Welcome animation when a workspace is set up (#22622)

## Desktop


https://github.com/user-attachments/assets/87999ff5-9257-4fed-90e0-781322b1db98

## Mobile



https://github.com/user-attachments/assets/0d115cb6-7bca-4229-8fde-0f188e862b00


Greets the user the moment they finish onboarding: a halftone Twenty
mark (brand purple) assembles from scattered particles, shimmers, then
bursts outward to reveal the freshly loaded workspace behind it. Plays
once, ~3s, with a reduced-motion fallback.

`PageChangeEffect` sets a transient `isWelcomeAnimationVisibleState`
atom at the onboarding to workspace redirect seam (gated by
`shouldShowWelcomeAnimationOnNavigate`); `WelcomeOverlay`, mounted in
`WorkspaceAppProviders`, plays it and clears it. Transient by design, so
it never replays on reload.

## Why a canvas rendered on another thread

The overlay plays at the exact moment the workspace mounts behind it,
which is one of the heaviest main-thread stretches in the app (metadata,
providers, first data fetch). Anything animating on the main thread
competes with that work:

- framer-motion and plain main-thread `requestAnimationFrame` visibly
stuttered and froze during the mount, because long tasks starve rAF.
- CSS keyframes stay smooth (they run on the compositor), but can't
drive a ~2900-particle halftone with per-particle physics (staggered
assemble, moving shimmer band, directional burst).

So the halftone runs as a Canvas 2D particle system inside a Web Worker,
drawing to an `OffscreenCanvas` transferred from the main thread. The
whole render loop lives off the main thread, so app-mount jank can't
reach it. A main-thread path is kept as a fallback for browsers without
`OffscreenCanvas` / `transferControlToOffscreen`, and Safari workers
(which lack rAF) fall back to a fixed-interval loop. The renderer is a
pure, DOM-free module so it bundles cleanly into the worker; dot colors
come from CSS vars read on the main thread and passed in.

Also fires for every onboarding completion path and skips the billing
`PlanRequired` detour.

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packages/twenty-front/src/modules/onboarding/utils/shouldShowWelcomeAnimationOnNavigate.ts

@@ -0,0 +1,16 @@
+import { OnboardingStatus } from '~/generated-metadata/graphql';
+
+type ShouldShowWelcomeAnimationOnNavigateArgs = {
+  onboardingStatus: OnboardingStatus | null | undefined;
+  isOnOnboardingPage: boolean;
+  isNavigatingToOnboardingOrAuthPath: boolean;
+};
+
+export const shouldShowWelcomeAnimationOnNavigate = ({
+  onboardingStatus,
+  isOnOnboardingPage,
+  isNavigatingToOnboardingOrAuthPath,
+}: ShouldShowWelcomeAnimationOnNavigateArgs): boolean =>
+  onboardingStatus === OnboardingStatus.COMPLETED &&
+  isOnOnboardingPage &&
+  !isNavigatingToOnboardingOrAuthPath;