v4.0.4.12 - Edition-aware updater + web client fixes

v4.0.4.12 — Edition-aware updater + web client fixes

Critical fix: the in-app updater now installs the MSI matching your current edition.
Previously, Full-edition users running the updater silently received the Multimedia MSI
side-by-side, leaving the Full edition behind. Full users running the updater on this
or any future release will now correctly upgrade Full -> Full.

Also in this release:

• Web client: rail (left settings panel) now scrolls; outgoing message bubbles wrap
  properly instead of collapsing one character per line
• Web client: mutual contact add — adding @handle creates a contact entry on both sides
  and live-notifies the other party via WebSocket (no refresh needed)
• Web client: disappearing-message TTL changes broadcast over WebSocket so both
  participants see the same indicator immediately
• Web client: local qrcode.min.js fallback so the invite QR renders even when CDNs
  are blocked
• Web client: tombstone deletes now also strip the message from the visible list
• Settings -> Tab Visibility now lists Platytalk, YARA Scanner, Encrypted Clipboard,
  and Credential Manager (previously hidden from the Visibility panel even though
  they exist as tabs)

Assets:

• PlatypusToolsSetup-v4.0.4.12.msi Full edition installer (Windows)
• PlatypusToolsMediaSetup-v4.0.4.12.msi Multimedia edition installer (Windows)
• PlatypusTools-Portable-win-x64-v4.0.4.12.exe Portable single-file EXE (Windows)
• PlatypusTools-{Full|Media}-{rid}-v4.0.4.12.{zip|tar.gz} Portable archives for
  win-x64, win-arm64, linux-x64, linux-arm64, osx-x64, osx-arm64