fix(security): make auth cookie name configurable, override per env

The auth cookie name was hardcoded to ZB.MOM.WW.ScadaBridge.Auth. Because
browser cookies are scoped by host+path but NOT by port, two ScadaBridge
clusters on the same host (the local docker stack on localhost:9000 and
docker-env2 on localhost:9100) shared one cookie jar: signing into one
overwrote the other's cookie, and since the clusters use different JWT
signing keys + separate Data Protection key rings, the overwritten side
could no longer validate its cookie and the session died.

Add SecurityOptions.CookieName (default = canonical ZB.MOM.WW.ScadaBridge.Auth,
blank falls back to the default) applied via the SecurityOptions-bound cookie
PostConfigure. Override it to ...Auth.env2 in both docker-env2 Central nodes so
the two local clusters no longer collide; the primary cluster keeps the default
so its live sessions and production are unaffected. Adds 3 Security.Tests cases.

docker-env2/central-node-b/appsettings.Central.json

@@ -34,7 +34,8 @@
       "JwtSigningKey": "scadabridge-env2-dev-jwt-signing-key-must-be-at-least-32-characters-long",
       "JwtExpiryMinutes": 15,
       "IdleTimeoutMinutes": 30,
-      "RequireHttpsCookie": false
+      "RequireHttpsCookie": false,
+      "CookieName": "ZB.MOM.WW.ScadaBridge.Auth.env2"
     },
     "Communication": {
       "DeploymentTimeout": "00:02:00",