Give every dashboard page its own URL and move add-forms into dialogs

Pages are served at /resources, /sites, /domains, /mail-egress, /alerts, /access, /logs,
/apps, /account and /server/*, with working links, reloads and back button. Mail egress,
alerts, access, users, organizations, SSO and DKIM follow the same header-button and dialog
pattern as the other pages.

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

paths_test.go

@@ -0,0 +1,34 @@
+package hammerhead
+
+import (
+	"os"
+	"regexp"
+	"testing"
+)
+
+// Every address the dashboard JavaScript navigates to must be served by the server, or a
+// reload on that page would 404.
+func TestDashboardPathsMatchThePage(t *testing.T) {
+	src, err := os.ReadFile("web/index.html")
+	if err != nil {
+		t.Fatal(err)
+	}
+	m := regexp.MustCompile(`TAB_PATH = \{([^}]*)\}`).FindSubmatch(src)
+	if m == nil {
+		t.Fatal("TAB_PATH not found in web/index.html")
+	}
+	paths := regexp.MustCompile(`'(/[a-z/-]+)'`).FindAllSubmatch(m[1], -1)
+	if len(paths) < 10 {
+		t.Fatalf("found only %d page paths", len(paths))
+	}
+	for _, p := range paths {
+		if !isDashboardPath(string(p[1])) {
+			t.Errorf("%s is a dashboard page but the server doesn't serve it", p[1])
+		}
+	}
+	for _, p := range []string{"/api/me", "/nope", "/server", "/server/nope"} {
+		if isDashboardPath(p) {
+			t.Errorf("%s should not serve the dashboard", p)
+		}
+	}
+}