fix(gateway): fix payload decoding endianness and skip preamble Switch temperature and CO2 decoding from little-endian to big-endian to match the Zephyr firmware implementation. Skip the 2-byte company id preamble (0xffff) at the start of the manufacturer data payload.

gateway/gateway.py

@@ -61,13 +61,14 @@ class Gateway:
         """Decode key/value pairs from BLE advertising payload.
 
         Format per firmware spec:
+          2 bytes preamble (company id = 0xffff) — skipped
           0x01 : window open (1 byte, 0 or 1)
           0x02 : humidity (1 byte, integer %)
-          0x03 : temperature (2 bytes, integer / 10 = degrees C)
-          0x04 : CO2 ppm (4 bytes, integer)
+          0x03 : temperature (2 bytes big-endian, integer / 10 = degrees C)
+          0x04 : CO2 ppm (4 bytes big-endian, integer)
         """
         result = {}
-        i = 0
+        i = 2  # skip 2-byte preamble (company id 0xffff)
         while i < len(data):
             key = data[i]
             i += 1
@@ -78,11 +79,13 @@ class Gateway:
                 result["humidity"] = data[i]
                 i += 1
             elif key == self.KEY_TEMP and i + 1 < len(data):
-                raw = int.from_bytes(data[i:i+2], byteorder='little')
+                # Temperature stored as integer * 10, big-endian
+                # Example: 25.3°C is stored as 253 (0x00FD)
+                raw = int.from_bytes(data[i:i+2], byteorder='big')
                 result["temp"] = raw / 10
                 i += 2
             elif key == self.KEY_CO2 and i + 3 < len(data):
-                result["co2_ppm"] = int.from_bytes(data[i:i+4], byteorder='little')
+                result["co2_ppm"] = int.from_bytes(data[i:i+4], byteorder='big')
                 i += 4
             else:
                 log.warning(f"Unknown key 0x{key:02x} at offset {i-1}")