Remove network.server from File Provider extensions (Mac App Store)

Part of: #9941

## Problem

Both `FileProviderExt.appex` and `FileProviderUIExt.appex` declare `com.apple.security.network.server`. This is confirmed in the release build via `codesign`.

This is unusual for extensions of these types:
- A file-syncing extension normally makes outbound connections only.
- A file-provider **UI** extension (showing action dialogs) has no obvious reason to listen on a port at all.

Apple reviewers will flag any `network.server` entitlement and request justification.

## Affected files

- `shell_integration/MacOSX/FileProviderExt.entitlements.cmake` (line 13)
- `shell_integration/MacOSX/FileProviderUIExt.entitlements.cmake`

## Required change

Audit whether either extension truly listens on a TCP/UDP port. If all traffic is outbound (sync to server), remove `network.server` from both. If the File Provider extension uses it for local XPC or socket communication, replace it with the appropriate entitlement or eliminate the need altogether.