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>

backend/src/api/gallery.rs

@@ -30,7 +30,7 @@ pub async fn list_all_gallery(
             "id": id,
             "catalog_id": &catalog_id,
             "filename": &filename,
-            "url": format!("/api/gallery/{}/{}", catalog_id, filename),
+            "url": format!("/api/gallery/files/{}/{}", catalog_id, filename),
             "caption": r.try_get::<Option<String>, _>("caption").unwrap_or_default(),
             "created_at": r.try_get::<i64, _>("created_at").unwrap_or_default(),
             "target_name": r.try_get::<Option<String>, _>("target_name").unwrap_or_default(),
@@ -60,7 +60,7 @@ pub async fn list_gallery(
             "id": id,
             "catalog_id": catalog_id,
             "filename": filename,
-            "url": format!("/api/gallery/{}/{}", catalog_id, filename),
+            "url": format!("/api/gallery/files/{}/{}", catalog_id, filename),
             "caption": r.try_get::<Option<String>, _>("caption").unwrap_or_default(),
             "created_at": r.try_get::<i64, _>("created_at").unwrap_or_default(),
         })
@@ -147,7 +147,7 @@ pub async fn upload_image(
         "id": id,
         "catalog_id": catalog_id,
         "filename": filename,
-        "url": format!("/api/gallery/{}/{}", catalog_id, filename),
+        "url": format!("/api/gallery/files/{}/{}", catalog_id, filename),
     })))
 }