fix: devicecheck biznis logika

API.md

@@ -140,10 +140,10 @@ Retrieve all devices in the system (public read access).
 ```
 
 **Status IDs**:
-- `1`: OK/Online
-- `2`: Warning
-- `3`: Error
-- `4`: Offline
+- `1`: ok
+- `2`: pending
+- `3`: lost
+- `4`: disabled
 
 ---
 
@@ -840,6 +840,57 @@ Devices can announce themselves by publishing to the discovery topic:
 
 ---
 
+### Device Check (State Polling)
+
+The server periodically publishes device check requests to the main MQTT topic and
+expects devices to respond on the same topic.
+
+**Topic**: `{configured_mqtt_topic}`
+
+**Request Message Published**:
+```json
+{
+  "type": "device_check_request",
+  "device_id": "uuid",
+  "requested_at": "2026-01-14T10:00:00Z"
+}
+```
+
+**Expected Device Response**:
+```json
+{
+  "type": "device_check_response",
+  "device_id": "uuid",
+  "status": "ok" | "lost" | "pending"
+}
+```
+
+---
+
+### Sensor Readings via MQTT
+
+Devices can publish sensor readings directly to the main MQTT topic. The server
+stores readings only if the `sensor_id` exists in the database.
+
+**Topic**: `{configured_mqtt_topic}`
+
+**Message Format**:
+```json
+{
+  "type": "sensor_reading",
+  "sensor_id": "uuid",
+  "value": 23.7,
+  "value_at": "2026-01-14T10:00:00Z"
+}
+```
+
+**Notes**:
+- `type` may also be `sensor_value`.
+- `value` may be a number, boolean, or numeric string (e.g., "1", "0", "23.7").
+- `value_at` is optional; if omitted, the server uses the current time.
+
+---
+
 ## Error Responses
 
 All endpoints may return the following standard error responses: