chore: bump version to 1.3.7

Rolls up the v1.3.6→1.3.7 fixes already on main:

- relay: drop the spurious old.Close() on s2c-ctrl rebind that was
  cascading "~1 min disconnect/reconnect" through whole QUIC connections
  on stable WAN (b33f7c1)
- pathinfo: record per-qualified-path (sum hop latencies, AND online
  flags) so AUB/cn-xinchang/2400 no longer shows just the first hop
  (24509fa)
- remote-proxy: carry peer auth on the inbound-only s2c-ctrl dial path
  so passthrough-enabled targets stop returning 404 and redirecting to
  /login (699bf66)

Bond multi-hop user-explicit exit_paths remains a known limitation —
filed in docs/bond-multihop-exit-paths-todo.md (gitignored). Out of
scope for this cycle.

Author: FrankoonG

internal/api/server.go

@@ -946,7 +946,7 @@ func (s *Server) getStats(w http.ResponseWriter, r *http.Request) {
 }
 
 // Version is the application version. Update this on each release.
-const Version = "1.3.6"
+const Version = "1.3.7"
 
 func init() {
 	app.AppVersion = Version