rename natus → sky across the codebase — natal chart abstraction is now sky throughout, since chart inputs aren't birthday-gated

Mechanical rename: 5 files (sky-wheel.js, _sky.scss, _sky_overlay.html, SkyWheelSpec.js x2), 24 in-place edits across templates/views/urls/SCSS/JS/tests/CLAUDE.md. URL names epic:natus_save → epic:sky_save (epic namespaced, no clash w. dashboard:sky_save), JS module NatusWheel → SkyWheel, DOM ids id_natus_* → id_sky_*, BEM classes natus-* → sky-*, dashboard sky_natus_data/sky_natus_preview collapsed to sky_data/sky_preview_data. No DB migration needed (User.sky_chart_data + GameEvent.SKY_SAVED already used sky-prefix). 778 ITs + Jasmine green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/apps/epic/models.py

@@ -653,7 +653,7 @@ class Character(models.Model):
         on_delete=models.SET_NULL, related_name='character_significators',
     )
 
-    # ── natus input (what the gamer entered) ─────────────────────────────
+    # ── sky input (what the gamer entered) ─────────────────────────────
     birth_dt    = models.DateTimeField(null=True, blank=True)   # UTC
     birth_lat   = models.DecimalField(max_digits=9, decimal_places=6, null=True, blank=True)
     birth_lon   = models.DecimalField(max_digits=9, decimal_places=6, null=True, blank=True)
@@ -662,7 +662,7 @@ class Character(models.Model):
         max_length=1, choices=HOUSE_SYSTEM_CHOICES, default=PORPHYRY,
     )
 
-    # ── computed natus snapshot (full PySwiss response) ───────────────────
+    # ── computed sky snapshot (full PySwiss response) ───────────────────
     chart_data  = models.JSONField(null=True, blank=True)
 
     # ── celtic cross spread (added at PICK SEA) ───────────────────────────