v0.9.4 — fewer false error banners + tidier group recovery

Seamless update from any 0.9.x build — same signing key, so F-Droid updates in place (no reinstall).

🐛 Fixes

• No more "welcome not addressed to this member" banner (#455). Adding a member broadcasts an
  MLS Welcome to the whole group, and every member who isn't the one being added would see a red
  banner for it — normal group traffic, not an actionable error. It's now filtered (same treatment
  as the 0.9.3 "No matching key package" fix), so the banner only shows for a real failure.

🔁 Other

• Tidier group recovery (#324/#433). When you tap "Ask to be re-added" after falling out of
  sync, the request now goes only to the group's creator — the one member who can actually
  re-add you — instead of being broadcast to everyone. Same experience for the person asking; less
  traffic, less metadata, and no stray recovery message landing in every other member's 1:1.