Fixed Android Enterprise page not refreshing (#45914)

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**Related issue:** Resolves #45862 

Speculative fixes since I wasn't able to repro issue locally.
Refresh AppContext and the React Query ["config"] cache directly after
the SSE/DELETE response so AndroidMdmCard and AndroidMdmPage flip
without a manual page reload, with a bounded retry to defeat the 1s
cached_mysql.AppConfig TTL. Also harden startSSE to detect the success
signal across chunk boundaries and reject (rather than hang) when the
stream ends without it.

# Checklist for submitter

If some of the following don't apply, delete the relevant line.

- [x] Changes file added for user-visible changes in `changes/`,
`orbit/changes/` or `ee/fleetd-chrome/changes`.
See [Changes
files](https://github.com/fleetdm/fleet/blob/main/docs/Contributing/guides/committing-changes.md#changes-files)
for more information.

- [x] Timeouts are implemented and retries are limited to avoid infinite
loops

## Testing

- [x] QA'd all new/changed functionality manually

For unreleased bug fixes in a release candidate, one of:

- [x] Confirmed that the fix is not expected to adversely impact load
test results

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## Summary by CodeRabbit

* **Bug Fixes**
* Fixed Android Enterprise page not refreshing after connecting or
disconnecting Android MDM. The Enterprise ID and card state now update
automatically without requiring a manual page reload.

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changes/45862-android-enterprise-page-refresh

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+- Fixed Android Enterprise page not refreshing after connecting or disconnecting Android MDM, so the Enterprise ID and card state are visible without a manual page reload.