Jevcast 1.21.1

Jevcast 1.21.1 fixes source builds on Xcode 26. This is a source release; no notarized app download is attached.

The Mail account sidebar now uses smaller SwiftUI expressions. This fixes the hosted compiler timeout without changing the layout or behavior. It includes all Mail features from 1.21.0. Background attachment reads initialize their storage path without entering the UI actor and avoid a nested detached task that stalled the older runtime.

Send Later requires Jevcast open and the Mac awake. Live delivery, cross-device draft handling, and provider alias acceptance remain separate acceptance checks.

Verification: the final code passed the complete local suite (1,184 tests, 3 intentional skips, 0 failures), a signed universal build, and GitHub Actions on Xcode 26.6. Demo snapshots verified the launcher-only Mail layout. No real mail was sent for testing.