fix: use consistent fallback pattern and clarify documentation

- Change protocol_version to use 'or' fallback pattern like other config values
- Update config.yaml.sample comment to clarify both quoted and unquoted values work
- Addresses Copilot feedback on PR #3

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

config.yaml.sample

@@ -4,7 +4,7 @@ mqtt:
   username: mqtt
   password: password
   qos: 0
-  protocol_version: "5"  # MQTT protocol version: "3.1.1" or "5" (default: "5")
+  protocol_version: "5"  # MQTT protocol version: 3.1.1/3 or 5 (with or without quotes, default: 5)
   prefix: amcrest2mqtt
   discovery_prefix: homeassistant
   tls_enabled: False

src/amcrest2mqtt/mixins/helpers.py

@@ -200,7 +200,7 @@ class HelpersMixin:
             "host":             str(mqtt.get("host")             or os.getenv("MQTT_HOST", "localhost")),
             "port":         int(str(mqtt.get("port")             or os.getenv("MQTT_PORT", 1883))),
             "qos":          int(str(mqtt.get("qos")              or os.getenv("MQTT_QOS", 0))),
-            "protocol_version": str(mqtt.get("protocol_version", os.getenv("MQTT_PROTOCOL", "5"))),
+            "protocol_version": str(mqtt.get("protocol_version") or os.getenv("MQTT_PROTOCOL", "5")),
             "username":         str(mqtt.get("username")         or os.getenv("MQTT_USERNAME", "")),
             "password":         str(mqtt.get("password")         or os.getenv("MQTT_PASSWORD", "")),
             "tls_enabled":     bool(mqtt.get("tls_enabled")      or (os.getenv("MQTT_TLS_ENABLED", "false").lower() == "true")),