[DOCS] Remove dead compatible.openmqttgateway.com links (#2205) (#2322)

The compatible.openmqttgateway.com site is offline (TLS connection reset),
leaving 38 dead links across the docs and README. Repoint BLE device lists
to the canonical Theengs Decoder devices page already used by the navbar,
point boards/devices/parts references to the corresponding docs pages, and
drop the affiliate-site mentions and 'Where to Buy' links that have no live
equivalent. Also fix a malformed markdown link in docs/use/ble.md.

docs/prerequisites/board.md

@@ -6,8 +6,6 @@ aside: false
 
 OpenMQTTGateway is not closed to one board or type of board, by using the power of the Arduino framework and libraries that are cross compatibles it let you many choice of hardware, from an ESP8266 to an ESP32.
 
-You can take a look to the [OpenMQTTGateway compatible website](https://compatible.openmqttgateway.com) to have a view of the [supported boards](https://compatible.openmqttgateway.com/index.php/boards/).
-
 Moreover the gateways capacities can be extended with sensors; DHT, HC SR501, ADC, I2C bus, INA226, MQ2, TEMT6000, TSL2561, BME280/BMP280, HTU21D, AHTx0, DS1820
 or actuators; LED, relays, PWM.
 
@@ -45,7 +43,6 @@ Support the project by purchasing the [Theengs bridge](https://shop.theengs.io/p
 The plug is available in North America only, other regions are planned.
 
 Choosing your board depends heavily on the technologies you want to use with it.
-To have a good overview of the compatibilities per board you can refer to the compatible modules attributes of each [board](https://compatible.openmqttgateway.com/index.php/boards/).
 
 The choice between these boards will depend on your knowledge and your requirements in terms of reliability, situation, modules wanted and devices you already have. Use the table below to explore the latest environments.