Fix 403 Error in LiveGenerativeModel due to missing Android Package headers

- Located the `getWebSocketSession` function in `APIController.kt`.
- Modified the function to ensure `applyHeaderProvider()` is called within the webSocketSession configuration block.
- Refactored header generation to `resolveHeaders` suspend function which is called before the block to handle Ktor's non-suspending configuration block.
- Applied resolved headers manually inside the block to ensure `X-Android-Package` and `X-Android-Cert` are present.
- Verified that headers are correctly attached with a test.

Author: google-labs-jules[bot]