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/ui/styles/radio.css

@@ -899,3 +899,132 @@
   padding-top: 3px;
   overflow-wrap: anywhere;
 }
+/* ── Local RTL-SDR card (FM + Local ADS-B receiver) ── */
+.sdr-radio-card {
+  display: grid;
+  gap: 7px;
+  margin-top: 3px;
+  padding: 9px;
+  border: 1px solid rgba(255, 170, 60, 0.28);
+  border-radius: 7px;
+  background: linear-gradient(
+    180deg,
+    rgba(31, 18, 4, 0.58),
+    rgba(4, 20, 24, 0.72)
+  );
+}
+.sdr-radio-heading,
+.sdr-radio-actions,
+.sdr-mode-row,
+.sdr-gain-row,
+.sdr-frequency-row,
+.sdr-seek-row {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+}
+.sdr-radio-heading {
+  justify-content: space-between;
+}
+.sdr-radio-heading strong {
+  color: #ffd38a;
+  font: 9px/1 var(--font-mono);
+  letter-spacing: 0.1em;
+}
+#sdr-connection-state {
+  color: #9e865f;
+  font: 7px/1 var(--font-mono);
+  letter-spacing: 0.1em;
+}
+#sdr-connection-state.active {
+  color: #74f7c4;
+}
+.sdr-radio-card > p {
+  margin: 0;
+  color: rgba(213, 230, 225, 0.58);
+  font: 7px/1.4 var(--font-mono);
+}
+.sdr-radio-card button,
+.sdr-radio-card select,
+.sdr-radio-card input[type='number'] {
+  min-height: 28px;
+  border: 1px solid rgba(255, 183, 82, 0.28);
+  border-radius: 5px;
+  color: #ffd79a;
+  background: rgba(38, 25, 8, 0.52);
+  font: 8px/1 var(--font-mono);
+}
+.sdr-radio-card button {
+  padding: 6px 8px;
+  cursor: pointer;
+}
+.sdr-radio-card button:hover:not(:disabled),
+.sdr-radio-card button:focus-visible:not(:disabled),
+.sdr-radio-card button.active {
+  border-color: #ffd38a;
+  color: #fff;
+  outline: none;
+  background: rgba(130, 83, 18, 0.28);
+}
+.sdr-radio-card button:disabled,
+.sdr-radio-card select:disabled {
+  opacity: 0.4;
+  cursor: not-allowed;
+}
+.sdr-radio-actions > *,
+.sdr-mode-row > *,
+.sdr-seek-row > * {
+  flex: 1;
+}
+.sdr-gain-row label,
+.sdr-frequency-row label {
+  color: #9e865f;
+  font: 7px/1 var(--font-mono);
+  letter-spacing: 0.08em;
+}
+.sdr-gain-row select {
+  flex: 1;
+  min-width: 0;
+  padding: 5px 7px;
+}
+.sdr-adsb-stats {
+  display: grid;
+  grid-template-columns: repeat(2, minmax(0, 1fr));
+  gap: 4px 8px;
+  color: #9e865f;
+  font: 7px/1.3 var(--font-mono);
+  letter-spacing: 0.08em;
+}
+.sdr-adsb-stats[hidden] {
+  display: none;
+}
+.sdr-adsb-stats output {
+  color: #ffd79a;
+  font: 9px/1 var(--font-mono);
+}
+.sdr-frequency-row input[type='number'] {
+  width: 78px;
+  min-width: 0;
+  padding: 5px 7px;
+}
+.sdr-frequency-row button {
+  margin-left: auto;
+}
+.sdr-radio-card .radio-volume-row {
+  color: #9e865f;
+}
+.sdr-radio-card .radio-playback-state {
+  color: #ddbe86;
+}
+.sdr-radio-card .radio-playback-state.error {
+  color: #ff9d8f;
+}
+.sdr-feed-status {
+  color: #9e865f;
+  font: 8px/1.3 var(--font-mono);
+  letter-spacing: 0.08em;
+  overflow-wrap: anywhere;
+}
+.sdr-feed-status[hidden] {
+  display: none;
+}