[fix](trx-wxsat): fix LRPT decoder always-enabled bug and implement image decoding

The LRPT decoder task was missing mode checks, processing audio in any
rig mode once toggled on. Now it only activates in FM mode, matching
the decoder registry descriptor. Also corrects active_modes from
DIG/USB to FM.

Replaces the MCU stub (which treated compressed JPEG data as raw
pixels) with proper Huffman + inverse-DCT decompression, CCSDS packet
reassembly from MPDUs, and CCSDS derandomization in the CADU framer.

https://claude.ai/code/session_0135LuveBndEiZHkU2jsKPB9
Signed-off-by: Claude <noreply@anthropic.com>

src/trx-protocol/src/decoders.rs

@@ -125,7 +125,7 @@ pub const DECODER_REGISTRY: &[DecoderDescriptor] = &[
         id: "lrpt",
         label: "Meteor LRPT",
         activation: DecoderActivation::Toggle,
-        active_modes: &["DIG", "USB"],
+        active_modes: &["FM"],
         background_decode: false,
         bookmark_selectable: true,
     },