SIENTIAPDE-2202

SIENTIAPDE-2202 Add gateway end-to-end test suite (e2e/)

End-to-end suite at the repo root, following the Laborious/Orchestrator
pattern: numbered scenarios per topic in e2e/scenarios.md (1:1 with
test_scenario_* functions), scenario inputs as JSON, Postgres DDL mirrored
from production, `integration` marker, excluded from the default pytest run.

Every dependency runs for real: MongoDB, Redis, PostgreSQL, MinIO and NATS
via testcontainers, OPC UA servers in process (asyncua). Pods are built from
the environment like ingestor/app.py and driven one loop iteration at a time.

69 scenarios across 7 topics: slot leasing and failover, subscription reads,
NATS writes and write_status (incl. the SIENTIAPDE-2202 timestamp/quality
matrix, checked on the server and on the wire), gRPC ReadTag, active reads,
client certificates/security, pod lifecycle.

Replaces tests/functional (legacy slot v1 tests, fully commented out) and
tests/functional/test_write_e2e.py (now scenarios 3.1.x).

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

e2e/scenario_inputs/slot_multi_name.json

@@ -0,0 +1,20 @@
+{
+  "plant-a": {
+    "name": "plant-a",
+    "server_id": "1",
+    "url": "@server:plant-a",
+    "subscription_period_ms": 100,
+    "security": {"mode": "None", "policy": "None"},
+    "certificate": null,
+    "tags": {
+      "ns=2;s=Pressure": {
+        "frequency": 1000,
+        "active_read": {"enabled": false},
+        "names": [
+          {"collection": "raw_furnace", "tag_name": "furnace_pressure", "model_id": "10", "model_name": "furnace"},
+          {"collection": "raw_boiler", "tag_name": "boiler_inlet_pressure", "model_id": "20", "model_name": "boiler"}
+        ]
+      }
+    }
+  }
+}