Add production config with LDAP, fix LDAP auth flow

- Production port: 3389
- LDAP enabled with theta42.com config
- Proper bind -> search -> user bind flow
- Support service account bind for user search
- Add systemd service file

conf/secrets.json

@@ -0,0 +1,14 @@
+{
+  "gateway": {
+    "token": "a41984619a5f4b9bf9148ab6eb4abca53eb796d046cbbec5"
+  },
+  "session": {
+    "secret": "dev-session-secret-change-in-production"
+  },
+  "auth": {
+    "ldap": {
+      "bindDN": "cn=ldapclient service,ou=people,dc=theta42,dc=com",
+      "bindPassword": "REPLACE_WITH_ACTUAL_PASSWORD"
+    }
+  }
+}