Whispr v1.1.13 — Whispr v1.1.13 — revert v1.1.12 chat sync change

Bug fix — revert v1.1.12

Reverts the chat-screen sync change shipped in v1.1.12.

That change tried to defend against a "phantom empty" race I suspected
on slower devices (Galaxy F23). After a thorough audit it turned out
to be the wrong fix:

1. The race I was guarding against doesn't actually exist in
   chat_provider.dart. openConversation resets _messages to
   [] but is gated by messagesLoading, and _loadMessages does
   an atomic reassignment — there's no path that briefly exposes an
   empty _messages while a conversation is open.

2. The guard fired on legitimate empty states: deleting the last
   message in a conversation, or clearing the chat while staying on
   the screen. The provider correctly emitted "no messages", but the
   screen kept showing the deleted bubble until you navigated away.

This release restores the v1.1.11 sync behaviour. Delete-last-message
and clear-chat update the screen immediately again.

Galaxy F23 vanishing-message issue

Still open. The v1.1.12 fix didn't address the actual root cause —
needs a logcat | grep -E "Chat|Flutter" from the F23 while
reproducing so we can tell whether it's a Flutter
ValueListenableBuilder quirk on the Mali GPU, a decryption
hash-mismatch on certain payloads, or something else. Investigation
continues; will not ship another fix until the cause is confirmed.

Verification

• Architecture: arm64-v8a
• Signed: release keystore (CN=Whispr)

SHA-256: 631b254d4eef0f08c1041819f3e4cf19972e2023762aed49c901cbe44d6de45d