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/db/mod.rs

@@ -17,6 +17,7 @@ pub async fn init_db(database_url: &str) -> anyhow::Result<SqlitePool> {
         .context("failed to connect to SQLite")?;
 
     run_schema(&pool).await?;
+    run_migrations(&pool).await?;
     seed_horizon(&pool).await?;
 
     Ok(pool)
@@ -34,6 +35,26 @@ async fn run_schema(pool: &SqlitePool) -> anyhow::Result<()> {
     Ok(())
 }
 
+/// Additive migrations for columns added after initial schema creation.
+/// SQLite doesn't support IF NOT EXISTS for ADD COLUMN, so we check the error and ignore it.
+async fn run_migrations(pool: &SqlitePool) -> anyhow::Result<()> {
+    let migrations: &[&str] = &[
+        "ALTER TABLE nightly_cache ADD COLUMN is_visible_tonight INTEGER DEFAULT 0",
+        "ALTER TABLE catalog ADD COLUMN caldwell_num INTEGER",
+        "ALTER TABLE catalog ADD COLUMN arp_num INTEGER",
+        "ALTER TABLE catalog ADD COLUMN melotte_num INTEGER",
+        "ALTER TABLE catalog ADD COLUMN collinder_num INTEGER",
+    ];
+    for sql in migrations {
+        match sqlx::query(sql).execute(pool).await {
+            Ok(_) => tracing::info!("Migration applied: {}", &sql[..sql.len().min(60)]),
+            Err(e) if e.to_string().contains("duplicate column") => {}
+            Err(e) => tracing::warn!("Migration skipped ({}): {}", sql, e),
+        }
+    }
+    Ok(())
+}
+
 async fn seed_horizon(pool: &SqlitePool) -> anyhow::Result<()> {
     let count: i64 = sqlx::query_scalar("SELECT COUNT(*) FROM horizon")
         .fetch_one(pool)