fix(planner): fix flip tile pointer events and selected ring hover

- backface-visibility hides elements visually but not to pointer events;
  disable pointer events on the hidden face explicitly so the X button
  on the back face is clickable and the front face doesn't intercept clicks
- Add .scene-selected:hover rule so green ring is not overwritten by the
  higher-specificity .scene:hover box-shadow

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

frontend/src/lib/planner/DesktopDayTile.svelte

@@ -237,6 +237,10 @@
 	.scene-selected {
 		box-shadow: 0 0 0 2px var(--green-dark), 0 6px 18px rgba(28,28,24,.14);
 	}
+	/* Keep ring visible on hover — :hover alone has higher specificity than .scene-selected */
+	.scene-selected:hover {
+		box-shadow: 0 0 0 2px var(--green-dark), 0 6px 18px rgba(28,28,24,.14);
+	}
 	.scene-dimmed {
 		opacity: 0.42;
 		pointer-events: none;
@@ -262,6 +266,10 @@
 		border-radius: 10px;
 		overflow: hidden;
 	}
+	/* backface-visibility hides visually but NOT pointer events — disable manually */
+	.card-back { pointer-events: none; }
+	.card.flipped .card-back { pointer-events: auto; }
+	.card.flipped .card-front { pointer-events: none; }
 
 	/* ── Front face ── */
 	.tile-overlay {