Invite links: starsync:// opens the app and asks to join; one app per profile; real invite address; clipboard pick-up

- starsync://host:port/?name=&pw= (PROTOCOL.md "Invite link"); the password only when ticked, never in logs
- Linux: launcher entry takes x-scheme-handler/starsync (%u, StartupNotify) and becomes its xdg-mime default; Windows: HKCU\Software\Classes\starsync -> starsync.exe
- InstanceLock: lock file + loopback handoff per profile folder; the running app comes up with the second start's activation token (Wayland/X11) or AllowSetForegroundWindow (Windows)
- Sharing looks up the internet address (HTTPS services with fallbacks); members card picks Internet / Home network / VPN and says when the port needs forwarding
- JoinOffers: link and clipboard prompt with /health, joins through ConnectFlow; dismissed clipboard invites kept as fingerprints

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -13,6 +13,10 @@ Links you put up are downloaded once for everyone, plus What's new and fixes for
 
 - What's new: the update band shows what changed, and after an update the app shows the full list once (also in Settings → About)
 - Sharper subtitles and picture: the video and its subtitles are drawn at your screen's resolution instead of the video's (Settings → Player → Sharp video and subtitles, on by default)
+- Invite links: Invite copies a starsync:// link; a friend clicks it (or just copies it and switches to Starsync) and the app asks "Join Bob's server?"
+- Invite finds your internet address, lets you pick it or your home-network address, and says when your router needs the port forwarded
+- The password goes into an invite link only when you tick "Include the password in the link"
+- Starsync runs once: a link clicked while it is open goes to the open window
 
 ### Changed