[feat](trx-frontend-http): add interactive Map tab with Leaflet

Add a Map sub-tab under Plugins that displays an interactive
OpenStreetMap via Leaflet.js showing:
- Receiver location (blue marker) from server config lat/lon
- APRS station positions (green markers) updated in real-time

The map lazy-initializes on first tab switch, handles tile rendering
on tab visibility changes, and deduplicates station markers by
callsign. Also includes the fallback snapshot lat/lon fields in the
API layer.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Stanislaw Grams <stanislawgrams@gmail.com>

src/trx-client/trx-frontend/trx-frontend-http/assets/web/style.css

@@ -212,6 +212,7 @@ small { color: var(--text-muted); }
 .sub-tab { background: transparent; border: none; border-bottom: 2px solid transparent; border-radius: 0; padding: 0.35rem 0.75rem; color: var(--text-muted); cursor: pointer; font-size: 0.85rem; height: auto; }
 .sub-tab.active { border-bottom-color: var(--accent-green); color: var(--accent-green); font-weight: 600; }
 .sub-tab:hover:not(.active) { color: var(--text); }
+#aprs-map { height: 400px; border-radius: 6px; }
 .aprs-controls { display: flex; gap: 0.6rem; align-items: center; margin-bottom: 0.75rem; }
 #aprs-packets { max-height: 360px; overflow-y: auto; border: 1px solid var(--border-light); border-radius: 6px; background: var(--input-bg); font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace; }
 .aprs-packet { font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace; font-size: 0.82rem; padding: 0.35rem 0.5rem; border-bottom: 1px solid var(--border); line-height: 1.4; }