MY SKY: dashboard applet + full-page natal chart — TDD

- User model: sky_birth_dt/lat/lon/place/house_system/chart_data fields (lyric migration 0018)
- Applet seed: my-sky (6×6, dashboard context) via applets migration 0009
- dashboard/sky/ — full monoapplet page: natus form + D3 wheel, LS key scoped to dashboard:sky; saves to User model
- dashboard/sky/preview/ — PySwiss proxy (same logic as epic:natus_preview, no seat check)
- dashboard/sky/save/ — persists 6 sky fields to User via update_fields
- _applet-my-sky.html: tile with h2 link to /dashboard/sky/
- 2 FTs (applet→link→form, localStorage persistence) + 12 ITs — all green

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

src/templates/apps/dashboard/_partials/_applet-my-sky.html

@@ -0,0 +1,6 @@
+<section
+    id="id_applet_my_sky"
+    style="--applet-cols: {{ entry.applet.grid_cols }}; --applet-rows: {{ entry.applet.grid_rows }};"
+>
+    <h2><a href="{% url 'sky' %}">My Sky</a></h2>
+</section>