Add full integration test with real Technitium DNS server

- Add docker-compose.integration.yml with Technitium + DDNS services
- Add full-integration-test.sh for end-to-end testing
- Add technitium-init.sh for automated zone/token setup
- Add comprehensive logging to DNS client
- Test creates real DNS records and verifies them in Technitium
- 8/9 tests passing with real DNS integration

docker-compose.integration.yml

@@ -0,0 +1,69 @@
+version: '3.8'
+
+services:
+  technitium:
+    image: docker.io/technitium/dns-server:11.0.2
+    container_name: technitium-dns
+    hostname: dns
+    ports:
+      - "5380:5380"
+    volumes:
+      - technitium-data:/etc/dns/config
+      - ./tests/integration/technitium-init.sh:/init.sh:ro
+    environment:
+      - DNS_SERVER_DOMAIN=dns.test.rip
+      - DNS_SERVER_ADMIN_PASSWORD=admin123
+      - DNS_SERVER_ADMIN_PASSWORD_FILE=
+      - DNS_SERVER_WEB_SERVICE_HTTP_PORT=5380
+      - DNS_SERVER_WEB_SERVICE_ENABLE_HTTPS=false
+      - DNS_SERVER_WEB_SERVICE_USE_SELF_SIGNED_CERT=false
+      - DNS_SERVER_OPTIONAL_PROTOCOL_DNS_OVER_HTTP=false
+      - DNS_SERVER_RECURSION=AllowOnlyForPrivateNetworks
+      - DNS_SERVER_LOG_USING_LOCAL_TIME=true
+    healthcheck:
+      test: ["CMD", "wget", "-q", "--spider", "http://localhost:5380/"]
+      interval: 10s
+      timeout: 5s
+      retries: 5
+      start_period: 30s
+    networks:
+      - dyn-test
+
+  dyn:
+    build: .
+    container_name: dyn-ddns-test
+    ports:
+      - "8080:8080"
+    volumes:
+      - dyn-data:/data
+    environment:
+      - SERVER_PORT=8080
+      - DATABASE_PATH=/data/dyn.db
+      - TECHNITIUM_URL=http://technitium:5380
+      - TECHNITIUM_TOKEN=dns-api-token-12345
+      - TECHNITIUM_USERNAME=
+      - TECHNITIUM_PASSWORD=
+      - BASE_DOMAIN=test.rip
+      - SPACE_SUBDOMAIN=space
+      - RATE_LIMIT_PER_IP=1000
+      - RATE_LIMIT_PER_TOKEN=1000
+      - TRUSTED_PROXIES=
+    depends_on:
+      technitium:
+        condition: service_healthy
+    healthcheck:
+      test: ["CMD", "wget", "-q", "--spider", "http://localhost:8080/"]
+      interval: 10s
+      timeout: 5s
+      retries: 3
+      start_period: 5s
+    networks:
+      - dyn-test
+
+volumes:
+  technitium-data:
+  dyn-data:
+
+networks:
+  dyn-test:
+    driver: bridge