Add target comparison modal, integration goal progress, and session planning + full catalog expansion

Features added this session:
- Target comparison: side-by-side overlay (CompareModal) from Targets page via ⊕ button on each row; shows altitude curves, key times, filter recommendations and per-filter integration progress for two targets simultaneously
- Integration goal progress dashboard card: per-target keeper minutes vs goal hours (from CLAUDE.md §16.3) broken down by filter, with color-coded progress bars; powered by new stats.integration_goals backend query
- Session planning timeline: Gantt-style "Plan Tonight" section on Dashboard (PlanningTimeline component) — search targets, set durations, sequential scheduling from dusk, overrun warnings, clipboard export
- Slew-optimized run order toggle (nearest-neighbor sort by RA/Dec angular distance)
- Best Nights 14-day card + Monthly Highlights card on Dashboard

Catalog expansions:
- Sharpless (Sh2), VdB, LDN, Barnard dark nebulae, LBN, Melotte, Collinder, Gum, RCW, Abell PN, Abell GC, PGC bright subset
- Caldwell/Arp/Melotte/Collinder number columns + cross-reference maps
- Weather score multiplier applied to composite sort
- galaxy_cluster type (ACO badge) throughout TypeBadge, CSS, filter chips

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/weather/DewAlert.tsx

@@ -1,3 +1,5 @@
+import { useEffect, useRef } from 'react';
+
 interface Props {
   level?: 'warning' | 'critical';
   temp?: number;
@@ -5,6 +7,31 @@ interface Props {
 }
 
 export default function DewAlert({ level, temp, dewPoint }: Props) {
+  const notifiedRef = useRef<string | null>(null);
+
+  // Trigger browser notification when dew alert level appears or escalates
+  useEffect(() => {
+    if (!level) return;
+    const key = level;
+    if (notifiedRef.current === key) return;
+    notifiedRef.current = key;
+
+    if (!('Notification' in window)) return;
+    const send = () => {
+      const margin = temp != null && dewPoint != null ? `Margin: ${(temp - dewPoint).toFixed(1)}°C. ` : '';
+      const body = level === 'critical'
+        ? `${margin}Condensation imminent — protect optics immediately.`
+        : `${margin}Enable dew heaters now.`;
+      new Notification('Astronome — Dew Alert', { body, tag: 'dew-alert' });
+    };
+
+    if (Notification.permission === 'granted') {
+      send();
+    } else if (Notification.permission !== 'denied') {
+      void Notification.requestPermission().then(p => { if (p === 'granted') send(); });
+    }
+  }, [level, temp, dewPoint]);
+
   if (!level) return null;
 
   const margin = temp != null && dewPoint != null ? (temp - dewPoint).toFixed(1) : null;