Alerts tab: fix hurricane/tropical storm bugs; rich alert cards matching the dashboard

Hurricane / tropical storm fixes
- NHC intensity is in knots: show real mph (80 kt = 92 mph) instead of mislabelled 'mph'
- Real Saffir-Simpson category from wind (was always cat 1); subtropical, post-tropical and
  potential-cyclone types no longer shown as 'depression'; each storm shows movement
  (direction + mph, previously a non-existent field), distance from you, update time, advisory link
- Forecast track points coloured by their own forecast strength (not the current class)
- Map click handlers registered once (popups stacked on every refresh); overlays wait for the
  map to settle instead of silently not drawing while tiles load; stale renders superseded
- Subtropical/tropical advice added to alert guidance; escaped storm names

Alert cards (active alerts only)
- What it's for, area, window, time remaining, plain-language meaning, what to do, and a
  Full details expander (headline, text, instructions, severity/urgency/certainty, issuer)
- No longer drops alerts beyond 6 per severity group; expired alerts are filtered out
- Shared plain-language alert glossary (alert-info.js, 64 products incl. tropical and surge)
  now used by both the app and the dashboard history

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

app/public/style.css

@@ -2429,13 +2429,14 @@ body.map-fs #unified-map {
   font-weight: 700;
   color: #fff;
 }
-.cat-td { background: #2196f3; }
-.cat-ts { background: #9c27b0; }
-.cat-1  { background: #ff9800; }
-.cat-2  { background: #f44336; }
-.cat-3  { background: #b71c1c; }
-.cat-4  { background: #7b1fa2; }
-.cat-5  { background: #1a237e; }
+.cat-td { background: #5dade2; }
+.cat-ts { background: #27ae60; }
+.cat-1  { background: #f1c40f; color: #1a1a1a; }
+.cat-2  { background: #f39c12; }
+.cat-3  { background: #e74c3c; }
+.cat-4  { background: #c0392b; }
+.cat-5  { background: #9b59b6; }
+.cat-ex { background: #95a5a6; }
 
 .hurricane-stats {
   display: flex;