[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/participate/support.md

@@ -12,7 +12,6 @@ If you like the project, you can help in different ways. Choose what fits you be
 
 ## Financial support
 - Purchase the [Theengs mobile application](https://app.theengs.io) or the [Theengs plug](https://shop.theengs.io).
-- Buy devices or parts via the [compatible web site](https://compatible.openmqttgateway.com) (affiliate links help the project).
 - Sponsor the project [developers](https://github.com/1technophile/OpenMQTTGateway/graphs/contributors).
 - Make a video or blog article about what you built with [OpenMQTTGateway](https://docs.openmqttgateway.com) and share it.