chore: strip pre-fork version comments across 72 files

Removes standalone "// v0.X.X:" comment lines and inline trailing
version annotations. Keeps version references in config field docs
and compatibility notes where they describe requirements.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/handlers/presence.go

@@ -6,7 +6,6 @@ package handlers
 // GET  /api/v1/presence?users=id1,id2 returns current status.
 // Online = last_seen within 90s.
 //
-// v0.29.0: Raw SQL replaced with PresenceStore + UserStore methods.
 
 import (
 	"net/http"