feat(gateway): optional .env loading for local dev (app + seed); document in e2e guide

docs/e2e-test-guide.md

@@ -20,6 +20,8 @@ Session script for validating the gateway against a real KepServer + cluster (wi
 
 ## 1. Seed test data
 
+Copy `.env.example` to `.env` (gitignored) and fill in the values from the session (OPC endpoint, Mongo/Redis/Postgres/MinIO accesses) — both the app and the seed script read it automatically (add `OPC_SERVER_URL=opc.tcp://HOST:49320`; it is seed-only, so it isn't in the example file). Then:
+
 ```bash
 python scripts/seed_e2e.py --print-only   # inspect first
 python scripts/seed_e2e.py                # seed Mongo + Redis slot v1 + Postgres table

ingestor/app.py

@@ -7,6 +7,13 @@ from time import time
 
 from prometheus_client import start_http_server
 
+try:  # optional: local dev reads .env; in-cluster env comes from Helm (no .env file)
+    from dotenv import load_dotenv
+
+    load_dotenv()
+except ImportError:
+    pass
+
 import ingestor.metrics as metrics
 from ingestor.config import GatewayConfig
 from ingestor.gateway_runtime import GatewayRuntime

requirements-dev.txt

@@ -16,4 +16,4 @@ pytest-asyncio>=0.21.0   # Async test support (already in main requirements)
 
 # Development Tools
 ipython>=8.12.0          # Enhanced Python shell
-ipdb>=0.13.13            # IPython debugger
+ipdb>=0.13.13            # IPython debuggerpython-dotenv>=1.0    # local dev only: app/seed read .env if present (in-cluster env comes from Helm)

scripts/seed_e2e.py

@@ -28,6 +28,13 @@ import json
 import os
 import sys
 
+try:  # optional: local dev reads .env; in-cluster env comes from Helm
+    from dotenv import load_dotenv
+
+    load_dotenv()
+except ImportError:
+    pass
+
 OPC_URL = os.getenv('OPC_SERVER_URL', 'opc.tcp://localhost:49320')
 
 CONNECTOR = {