fix(a11y): draw an unfavourited track as an outline, not a dimmer fill

`favCtrl.iconName` returned the solid glyph in both states, so "not a
favourite" was a filled heart in a duller colour and the only thing
separating the two states was hue. That fails outright for anyone who
cannot tell the two colours apart (WCAG 1.4.1), and reads as
"everything is a favourite" to everyone else.

`iconFor(favorited)` returns the outline or the fill, and the nine
`<wa-icon>` call sites split into the two cases they always were. The
three that show a *state* -- the mini player, the phone's now-playing
view, and the sidebar's marker for the favourites playlist itself --
pass it. The rest are context-menu items, which are actions rather than
states and take the outline `iconName` still returns.

`track-list` and `album-dropdown` already had this right, from inline
SVG paths of their own; this is the same rule for the call sites that
go through the icon library. `regular/star` is vendored to go with
`regular/heart`, which was already there.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MeQt5hgXg5YGoNZQ9ozG7L

frontend/src/components/now-playing-view/now-playing-view.ts

@@ -307,7 +307,7 @@ export class NowPlayingView extends LitElement {
                         : `Add ${track.title} to ${this.favCtrl.playlistName}`}
                     @click=${this.toggleFavorite}
                 >
-                    <wa-icon name=${this.favCtrl.iconName}></wa-icon>
+                    <wa-icon name=${this.favCtrl.iconFor(favorited)}></wa-icon>
                 </button>
             </div>
 

frontend/src/components/now-playing/now-playing.ts

@@ -527,7 +527,7 @@ export class NowPlaying extends LitElement {
                       )}
                 >
                   <wa-icon
-                    name=${this.favCtrl.iconName}
+                    name=${this.favCtrl.iconFor(isFav)}
                     variant=${favVariant}
                   ></wa-icon>
                 </button>

frontend/src/components/playlist-view/playlist-view.ts

@@ -1756,7 +1756,7 @@ export class PlaylistView extends ViewLifecycleMixin(LitElement) {
                     ${entry.summary.ID === this.favCtrl.playlistId
                         ? html`<wa-icon
                               class="playlist-icon"
-                              name=${this.favCtrl.iconName}
+                              name=${this.favCtrl.iconFor(true)}
                           ></wa-icon>`
                         : entry.summary.IsSmart
                           ? html`<wa-icon