Update relay-handling logic and test assertions for device binding and local IP resolution

- Correct test cases to ensure proper relay IDs are switched.
- Add robust local IP resolution for relay-device bindings, including caching and inventory backfill.
- Introduce fast-path options for relay status and switch dispatch.
- Validate PHP extensions (`curl`, `sqlite3`) in edge agent images.

services/edge-agent/Dockerfile.test-gateway

@@ -3,9 +3,7 @@ FROM php:8.2-cli
 WORKDIR /opt/truckwash-edge-agent
 
 RUN set -eux; \
-    apt-get update; \
-    apt-get install -y --no-install-recommends ca-certificates; \
-    rm -rf /var/lib/apt/lists/*
+    php -r 'foreach (["curl", "sqlite3"] as $extension) { if (!extension_loaded($extension)) { fwrite(STDERR, "Missing PHP extension: {$extension}\n"); exit(1); } }'
 
 COPY services/nginx/app/resources/edge-gateway-agent/ ./