[fix](trx-frontend-http): put HF APRS on the map, under its own source

The HF APRS list never plotted anything.  Its plugin ships in the map plugin
group and its packets carry positions, but nothing ever handed one to the
map, so a station heard on 30 m appeared in the panel and nowhere else — and
unlike the replay gaps around it, no reload brought it back.

Plot it, and not as more VHF APRS.  HF is a different band and a different
path, and lumping the two together would leave no way to tell them apart or
to look at one without the other, so it goes on as a source of its own: its
own colour, its own chip in the map's Show filter, its own entry in the
source legend, and its own clear.

Station entries are keyed by source and callsign rather than callsign alone,
so a station worked on both bands keeps a marker for each while the popups,
the search text and the tracks still show the callsign as heard.

decode-flow feeds an HF beacon alongside the VHF one and checks all of it:
both reach the map under their own sources, the Show row offers HF APRS next
to APRS, and turning that chip off takes the HF station off the map while the
VHF one stays.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SyX26FCpMQxiBoC7r5K1A7
Signed-off-by: Stan Grams <sjg@haxx.space>

docs/User-Manual.md

@@ -464,7 +464,7 @@ and each page answers that differently:
 |------|-------|
 | Radio | The selected rig: its spectrum, its audio, and the mini decode views over the waterfall. |
 | Digital Modes | The selected rig: every decoder panel, its counts and its status line. |
-| Map | The whole station — every rig's positions, with the map's own rig filter to narrow it. |
+| Map | The whole station — every rig's positions, with the map's own rig filter to narrow it. HF APRS is a source of its own there, filtered apart from VHF APRS. |
 | Statistics | The whole station, including the per-rig comparison. |
 
 Switching rigs repaints the radio and digital modes pages for the rig now