feat(sdr): local receivers — browser RTL-SDR, Local ADS-B layer and decoder feeds (#732)

Adds a Local ADS-B layer fed by your own receivers: a browser WebUSB
RTL-SDR (with FM listening) and local 1090/978 MHz decoder feeds
(LOCAL_RECEIVER_FEEDS, local and private addresses only). Local aircraft
draw in magenta with class, silhouettes, 3D models, trails and a position
sanity filter; the click card names the band and input that heard them.

Builds on Sameh Khamis's SDR prototype and the initial GEV port by
Mazeyar Moeini Feizabadi (#134); the decoder-feed design follows the
notes on #57. Closes #57.

Co-authored-by: Sameh Khamis <[email protected]>
Co-authored-by: Mazeyar Moeini Feizabadi <[email protected]>

src/data/fixtures/README.md

@@ -7,3 +7,16 @@
   (22,980 bytes). Used by offline decode/source tests and the explicit `qa-traffic --fixtures`
   browser mode — it is a point-in-time congestion snapshot, not a bundled
   data layer, and is never loaded by ordinary application startup. © TomTom.
+- `adsb-austin-frames.txt` — 112 raw Mode S frames (`*<hex>;`, one per line,
+  in receive order) received over Austin, TX, and
+  `adsb-austin-dump1090-aircraft.json` — dump1090-fa's `aircraft.json` decode
+  of the same frames, trimmed to the fields the tests assert on. Used by the
+  Local ADS-B decoder and record-adapter tests; never loaded at runtime.
+- `adsb-austin-capture-timed.json` — a second ~90 s receive over Austin, TX:
+  846 extended squitters from six aircraft (`frames`: `[ms, hex]`), with
+  dump1090-fa's decoded positions and emitter categories for the same
+  interval (`dump1090`: per ICAO `flight`, `category` and `fixes` as
+  `[ms, lat, lon]`). The capture has no per-frame timestamps; each frame's
+  time is interpolated between the frames whose decoded position equals a
+  dump1090 fix, timed as dump1090's `now − seen_pos`. Used by the decoder's
+  category, speed-check and track-accuracy tests; never loaded at runtime.