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/db_schema.sql

@@ -0,0 +1,33 @@
+-- =============================================================================
+-- E2E test database schema for the ``sientia_data`` namespace.
+--
+-- Mirrors the production DDL one-to-one so any change in production can be
+-- pasted directly into this file. The conftest fixture drops the schema and
+-- loads this SQL into the testcontainers Postgres before every test.
+--
+-- The gateway only touches ``sientia_data.predictions``: it updates
+-- ``write_status`` (contract C3, SIENTIAPDE-1975) on the row the Laborious
+-- inserted. Same DDL as ``sientia-dataops-laborious/e2e/db_schema.sql``.
+-- =============================================================================
+
+CREATE SCHEMA IF NOT EXISTS sientia_data;
+
+-- -----------------------------------------------------------------------------
+-- sientia_data.predictions
+-- -----------------------------------------------------------------------------
+CREATE TABLE IF NOT EXISTS sientia_data.predictions (
+    model_id              int4 NOT NULL,
+    prediction            numeric NULL,
+    prediction_confidence numeric NOT NULL,
+    response_time         numeric NOT NULL,
+    prediction_status     text NOT NULL,
+    "timestamp"           timestamptz NOT NULL,
+    created_at            timestamptz DEFAULT CURRENT_TIMESTAMP NOT NULL,
+    "comments"            text NULL,
+    metadata_id           varchar(24) NULL,
+    write_status          text NULL,
+    CONSTRAINT unique_model_id_timestamp
+        UNIQUE (model_id, "timestamp"),
+    CONSTRAINT chk_predictions_write_status
+        CHECK (write_status IN ('pending', 'ok', 'error', 'session_bad'))
+);