app: replace `Fusion = any` placeholder type in types.ts with a proper definition

In `packages/modules/app/src/types.ts`, the `Fusion` type is aliased to `any` as a placeholder:

```ts
// biome-ignore lint/suspicious/noExplicitAny: TODO - needs proper type definition
type Fusion = any;
```

Define a proper shape for `Fusion` instead of using `any`.

Start in packages/modules/app/src/types.ts and inspect every usage of the Fusion alias to determine the values and properties the module expects. Trace those usages to their source types or APIs before defining the shape. Done means Fusion no longer uses any and the TypeScript checks still pass.

Written by the indexing model from the issue text.