Tweaks discovered when using Compound overrides. (#4456)

- Fixes a bug where gradients wouldn't use the latest tokens after first use.
- Makes the bloom aware of colour overrides (and discovers a bug with dark mode).
- Decouples HomeScreenCell from the HomeScreenViewModel.Context (so it can be previewed with colour overrides).

project.yml

@@ -72,7 +72,7 @@ packages:
     # path: ../matrix-rust-sdk
   Compound:
     url: https://github.com/element-hq/compound-ios
-    revision: 8d7ca2e413026735b724044847ff1ae3b40563f0
+    revision: 4ad0bd0acd825a905bb4955b32979fe34cc538eb
     # path: ../compound-ios
   AnalyticsEvents:
     url: https://github.com/matrix-org/matrix-analytics-events