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)

frontend/js/map.js

@@ -1645,6 +1645,18 @@ function encStyle(feature, resolution) {
     }
   }
 
+  // Safety net: if any draw function threw, canvas may be null. Fall back to
+  // a small colored circle so the feature is still visible and clickable.
+  if (!canvas) {
+    const fc = document.createElement('canvas'); fc.width = fc.height = 16;
+    const fx = fc.getContext('2d');
+    fx.beginPath(); fx.arc(8, 8, 7, 0, Math.PI * 2);
+    fx.fillStyle = colours[0] ? _s57css(colours[0]) : '#607d8b'; fx.fill();
+    fx.strokeStyle = '#fff'; fx.lineWidth = 1.5; fx.stroke();
+    canvas = fc;
+    console.warn('[ENC] canvas fallback for', layer, aidType, colours);
+  }
+
   // Compute zoom from resolution (deterministic, no map object access needed).
   // OL WebMercator: resolution ≈ 156543 / 2^zoom → zoom = log2(156543/res)
   const _zr = resolution ? Math.log2(156543.03392 / Math.max(resolution, 0.001)) : 14;
@@ -2005,46 +2017,69 @@ window.loadChartFeatures = async function() {
     const fc = await r.json();
     if (!fc.features?.length) return;
 
-    // Merge LIGHTS into co-located structures. NOAA codifies a buoy and its
-    // light as two features at the same coords. The structure often lacks
-    // COLOUR / CATLAM while the light carries it — we backfill the structure
-    // with the light's colour, then drop the (now redundant) LIGHT_POINT.
-    const structByKey = new Map();   // coordKey → structure feature
+    // ── Merge LIGHTS into nearby structure features ────────────────────────
+    // S-57 encodes each buoy/beacon and its light as TWO separate objects.
+    // They may be at exactly the same coordinates (NOAA pattern) or up to
+    // ~50 m apart (≈0.00045°). We try exact match first, then proximity.
+    // After merging: light attrs copied into host, LIGHT_POINT dropped.
+    const MERGE_DEG = 0.00045;   // ~50 m — matches backend proximity radius
+    const structList = [];       // [{ f, x, y }] — all structure features
     for (const f of fc.features) {
       const lyr = (f.properties?.layer || '').toUpperCase();
       if (lyr.startsWith('BOY') || lyr.startsWith('BCN') || lyr === 'LNDMRK') {
-        const c = f.geometry.coordinates;
-        structByKey.set(`${c[0].toFixed(6)}_${c[1].toFixed(6)}`, f);
+        const [x, y] = f.geometry.coordinates;
+        structList.push({ f, x, y });
       }
     }
+    // Fast exact-coord lookup (grid key rounded to 6 dp ≈ 0.11 m)
+    const structByKey = new Map();
+    for (const s of structList) {
+      structByKey.set(`${s.x.toFixed(6)}_${s.y.toFixed(6)}`, s.f);
+    }
+
     const before = fc.features.length;
     fc.features = fc.features.filter(f => {
       if (f.properties?.aid_type !== 'LIGHT_POINT') return true;
-      const c = f.geometry.coordinates;
-      const host = structByKey.get(`${c[0].toFixed(6)}_${c[1].toFixed(6)}`);
-      if (!host) return true;   // standalone light — keep
-      // Backfill host colour from light if missing
+      const [lx, ly] = f.geometry.coordinates;
+
+      // 1) Try exact coordinate match
+      let host = structByKey.get(`${lx.toFixed(6)}_${ly.toFixed(6)}`);
+
+      // 2) Proximity fallback (~50 m radius)
+      if (!host) {
+        let bestDist = MERGE_DEG;
+        for (const s of structList) {
+          const d = Math.sqrt((lx - s.x) ** 2 + (ly - s.y) ** 2);
+          if (d < bestDist) { bestDist = d; host = s.f; }
+        }
+      }
+
+      if (!host) return true;   // standalone light with no nearby structure — keep
+
       const hp = host.properties;
       const lp = f.properties;
+
+      // Backfill colour from light if host has none
       if (!hp.colours?.length && lp.colours?.length) {
         hp.colours = lp.colours.slice();
-        // Re-classify host now that we have colour info → infer CATLAM
+        // Infer CATLAM from colour when missing
         const region = hp.cell_region || 'B';
         const ialaB  = region === 'B';
         const c0 = lp.colours[0];
         if (!hp.catlam) {
-          if (c0 === 4) hp.catlam = ialaB ? 1 : 2;     // green → port in B, stbd in A
-          else if (c0 === 3) hp.catlam = ialaB ? 2 : 1; // red   → stbd in B, port in A
+          if (c0 === 4) hp.catlam = ialaB ? 1 : 2;
+          else if (c0 === 3) hp.catlam = ialaB ? 2 : 1;
         }
-        // Update aid_type to reflect inferred lateral significance
         if (hp.catlam === 1) hp.aid_type = 'LATERAL_PORT';
         else if (hp.catlam === 2) hp.aid_type = 'LATERAL_STBD';
       }
-      // Carry light attributes (character, range, height) into the host for the popup
+      // Copy light character, range, height → these appear in the tooltip
       if (lp.light_desc && !hp.light_desc) hp.light_desc = lp.light_desc;
       if (lp.range_nm   && !hp.range_nm)   hp.range_nm   = lp.range_nm;
       if (lp.height_m   && !hp.height_m)   hp.height_m   = lp.height_m;
-      return false;   // drop the light, host now represents it
+      // Copy orient so the buoy/beacon can anchor its leading line correctly
+      if (lp.orient != null && hp.orient == null) hp.orient = lp.orient;
+      return false;   // drop the now-redundant LIGHT_POINT
     });
     const dropped = before - fc.features.length;