fix(data): light info (LITCHR/range/height) en boyas y balizas de orilla

frontend/js/map.js:
- Reemplaza merge exacto por merge de proximidad (~50m) en loadChartFeatures
  para capturar pares LIGHTS/BOYLAT con coordenadas no exactamente iguales
- Guard null-canvas en encStyle con fallback visible + console.warn
- Mejora JS de debug: log layer/aidType cuando usa fallback

backend/services/chart_manager.py:
- Expande extraccion de light_desc a category buoy+beacon+landmark
  (antes solo BOYLAT/BOYCAR; BCNLAT/BCNWTW/LNDMRK perdian LITCHR silenciosamente)

backend/services/chart_manager.py

@@ -271,7 +271,10 @@ def _parse_cell(enc_path: Path) -> list[dict]:
                 "colours":  colours,           # list of S-57 colour codes
                 "colour_code": colours[0] if colours else None,  # primary colour
             }
-            if category == "light" or layer_name in ("BOYLAT","BOYCAR","BOYISD","BOYSPP","BOYSAW"):
+            # Extract light description for ALL navigational aids and lights.
+            # Previously only BOY* layers were included, so BCNLAT/BCNWTW/LNDMRK
+            # silently lost their LITCHR/SIGPER/VALNMR — fixed here.
+            if category in ("light", "buoy", "beacon", "landmark"):
                 props["light_desc"] = _light_desc(row)
             if layer_name.startswith("BOY") or layer_name.startswith("BCN"):
                 shape = _safe(row.get("BOYSHP"))