Move the route proxy into its module and run it from the trust image, on mesh-sdk's public membership (issues 1633, 1634, 1635)

A bundle is built only from its module's directory (ADR 0480 clause 4), so the proxy leaves
examples/ and the controller's internal/broker; the broker keeps no second copy of what the
proxy shares with mesh-sdk. The image and its Dockerfile go, and a test holds that only
build-agent declares one (clause 11).

modules/route-proxy/cmd/route-proxy/forwarded_test.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"crypto/tls"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"testing"
+)
+
+// A backend behind the proxy learns the client used TLS and which name it asked for, so the addresses
+// it writes into its own pages are the ones a client can use (2026-10-03: a forge's Go import tag
+// named an http clone URL, and Go refused the module path).
+func TestABackendIsToldTheRequestWasHTTPSAndForWhichName(t *testing.T) {
+	var proto, host, fwdHost, fwdFor string
+	backend := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		proto, host, fwdHost, fwdFor = r.Header.Get("X-Forwarded-Proto"), r.Host, r.Header.Get("X-Forwarded-Host"), r.Header.Get("X-Forwarded-For")
+	}))
+	defer backend.Close()
+	where, _ := url.Parse(backend.URL)
+	req := httptest.NewRequest(http.MethodGet, "https://git.example.org/novox/mesh-sdk/go?go-get=1", nil)
+	req.TLS = &tls.ConnectionState{}
+	req.Host = "git.example.org"
+	req.RemoteAddr = "192.0.2.7:51000"
+	towards(where).ServeHTTP(httptest.NewRecorder(), req)
+	if proto != "https" || fwdHost != "git.example.org" || host != "git.example.org" || fwdFor != "192.0.2.7" {
+		t.Errorf("the backend was told proto=%q host=%q forwarded-host=%q for=%q", proto, host, fwdHost, fwdFor)
+	}
+}