fix(add-playlist): align dialog head with content padding

The custom .apd-head was getting visually orphaned from the rest of the
dialog body: zero horizontal padding so the title sat flush against the
dialog edge (cards inside mat-dialog-content are inset by 24px), plus a
~44px vertical gap above the title even though the head reported
padding: 0.

The gap was Material's .mdc-dialog__title::before — a 40px-tall
invisible inline element used to baseline-align dialog titles to a
grid. Useful for single-line titles, hostile to a two-line head with
explicit subtitle.

Set .apd-head padding to 20px 24px 4px so it shares the dialog
content's 24px horizontal rhythm, then suppress the ::before ghost.
Title now sits 20px from the dialog top edge with the same left inset
as the method cards and the form fields below.

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

libs/playlist/import/feature/src/lib/add-playlist-dialog/add-playlist-dialog.component.scss

@@ -18,12 +18,21 @@
 }
 
 // ─── Dialog head (title + helper subtitle) ──────────────────────────────────
+// `mat-dialog-title` carries Material's `.mdc-dialog__title` defaults, which
+// include a 40px-tall `::before` ghost element for baseline alignment plus a
+// 6px/9px asymmetric padding. Both fight our custom two-line head — kill the
+// ghost and apply explicit padding so the title shares the same 24px
+// horizontal inset as `mat-dialog-content` below.
 .apd-head {
     display: flex;
     flex-direction: column;
     gap: 4px;
-    margin: 0 0 8px;
-    padding: 0;
+    margin: 0;
+    padding: 20px 24px 4px;
+
+    &::before {
+        display: none;
+    }
 }
 
 .apd-title {