Android KMP Paywall Events are sent to the Production Amplitude project instead of Sandbox and use incorrect platform value (android instead of Android)

[tsushanth]

Change WORKFLOW_CONTEXT_PLATFORM from "android" to "Android" in BackendEvent.Workflows.Context to fix the incorrect platform value sent with KMP paywall workflow events.

Scoped to just the platform-casing bug. The original report also mentions KMP paywall events being sent to the Production Amplitude project instead of Sandbox — that's a separate, unrelated issue and will be tracked/fixed in its own PR rather than bundled in here.

Found via automated repo scanning, fix written and reviewed before opening.

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Note

Low Risk
Single string constant and test expectation change for analytics payload casing only; no auth, billing, or runtime behavior changes.

Overview
Fixes the context.platform value on serialized workflow backend events (KMP paywall workflow lifecycle) so it is "Android" instead of "android", matching the expected khepri / WorkflowsEvent wire shape.

The default comes from WORKFLOW_CONTEXT_PLATFORM in BackendEvent.Workflows.Context; workflow serialization tests were updated to assert "Android" in encoded JSON.

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