test(integration): reorganize test structure and add runner script

- Move integration tests and mock upstream resources from `integration/` to `test/` directory.
- Add `test/integration.sh` script to orchestrate environment setup and test execution.
- Update build context in `docker-compose.integration.yml` to match new structure.
- Add documentation for local development and integration testing workflows in README.

test/integration_test.sh

@@ -0,0 +1,55 @@
+#!/bin/bash
+
+# Colors
+GREEN='\033[0;32m'
+RED='\033[0;31m'
+NC='\033[0m'
+
+echo "Starting Integration Test..."
+
+# 1. Wait for services
+echo "Waiting for services to be ready..."
+sleep 10 # Simple wait, in real world use health checks
+
+# 2. Create Key via Control Plane (ez-api)
+echo "Creating Key via ez-api..."
+KEY_SECRET="sk-test-integration-$(date +%s)"
+# Note: Keys route by group now; omitting group defaults to "default".
+RESPONSE=$(curl -s -X POST http://localhost:8080/keys \
+  -H "Content-Type: application/json" \
+  -d "{\"key_secret\": \"$KEY_SECRET\", \"balance\": 100.0, \"group\": \"default\"}")
+
+echo "Create Key Response: $RESPONSE"
+
+if [[ $RESPONSE == *"KeySecret"* ]]; then
+    echo -e "${GREEN}Key Created Successfully${NC}"
+else
+    echo -e "${RED}Failed to Create Key${NC}"
+    exit 1
+fi
+
+# 3. Verify Auth via Data Plane (balancer)
+echo "Verifying Auth via balancer..."
+# Note: We are hitting /v1/chat/completions. Since we don't have a real upstream, 
+# we expect 502 Bad Gateway (if upstream is down) or 404/200 from upstream.
+# But definitely NOT 401 Unauthorized.
+
+HTTP_CODE=$(curl -s -o /dev/null -w "%{http_code}" -X POST http://localhost:8081/v1/chat/completions \
+  -H "Authorization: Bearer $KEY_SECRET" \
+  -H "Content-Type: application/json" \
+  -d "{\"model\": \"gpt-3.5-turbo\", \"messages\": [{\"role\": \"user\", \"content\": \"Hello\"}]}")
+
+echo "Balancer HTTP Code: $HTTP_CODE"
+
+if [[ "$HTTP_CODE" == "401" ]]; then
+    echo -e "${RED}Auth Failed: Got 401 Unauthorized${NC}"
+    exit 1
+elif [[ "$HTTP_CODE" == "502" || "$HTTP_CODE" == "200" || "$HTTP_CODE" == "404" ]]; then
+    # 502 means Auth passed but upstream failed (expected in test env without real internet/upstream)
+    echo -e "${GREEN}Auth Passed (Upstream response: $HTTP_CODE)${NC}"
+else
+    echo -e "${RED}Unexpected Response: $HTTP_CODE${NC}"
+    exit 1
+fi
+
+echo -e "${GREEN}Integration Test Passed!${NC}"