ip.bind: bind outbound connections to the configured address (#9834)

* ip.bind: bind outbound connections to the configured address

-ip.bind only governed listeners; outbound gRPC and HTTP connections let
the OS pick the source IP, which may not even be able to reach the
target. Mirror the bind address into a process-global source address and
apply it to outbound TCP dials: the gRPC context dialer, the per-client
HTTP transports, and the default transport. Loopback targets and unix
sockets keep the OS-chosen source so same-host traffic still works.

* ip.bind: first-write-wins source IP, skip on address-family mismatch

Make SetOutboundLocalIP first-write-wins so a `weed server` component's own
bind setting (run in its goroutine) can't clobber the process-wide source
address the top-level -ip.bind already established for the other components.

Skip source binding when the target is a literal IP of a different family
than the bind address, since forcing a mismatched source fails the dial.

weed/command/webdav.go

@@ -89,6 +89,8 @@ func (wo *WebDavOption) resolvePaths() {
 
 func (wo *WebDavOption) startWebDav() bool {
 
+	util.SetOutboundLocalIP(*wo.ipBind)
+
 	// detect current user
 	uid, gid := uint32(0), uint32(0)
 	if u, err := user.Current(); err == nil {