feat: implement MoloApp plans 01-15 with integration

Full C++23 framework tree: runtime, observability, security,
data, app, realtime, supervisor, clients, CLI, example plus
enterprise tenancy, audit, operability, governance,
supplychain. Postgres via docker compose for tests.

tests/example/validate/user_test.cpp

@@ -0,0 +1,21 @@
+// Route: POST /validate/user  (all-failures validation error)
+#include "support/Assert.hpp"
+
+using namespace molo::example::test;
+
+int main() {
+  Fixture f;
+  auto ok = f.client->post(
+      "/validate/user",
+      "{\"username\":\"ada\",\"email\":\"ada@x.io\",\"age\":\"36\"}",
+      "application/json");
+  check(ok.status == 200, "valid model is 200");
+  auto bad = f.client->post("/validate/user",
+                            "{\"username\":\"ad\",\"age\":\"old\"}",
+                            "application/json");
+  check(bad.status == 422, "invalid model is 422");
+  check(contains(bad.body, "username"), "username failure listed");
+  check(contains(bad.body, "email"), "missing email listed");
+  check(contains(bad.body, "age"), "bad age listed");
+  return finish("validate/user");
+}