feat(08-04): convert sidebar em-based spacing to px and apply icon/type tokens

- Sidebar: convert all em-based padding/gap to px values, icon sizes to --yj-icon-md
- Now-playing: cover placeholder icon to --yj-icon-lg, text sizes to type tokens
- Search-bar: search icon to --yj-icon-sm, input font to --yj-text-md
- Audio-player: convert em-based gap/padding/margin to px values
- Seek-bar: tooltip font to --yj-text-lg, margin from em to px
- Volume-control: padding/margin from em to px, thumb sizes from em to px
- All components import designTokens and include in static styles

frontend/src/components/audio-player/audio-player.ts

@@ -3,20 +3,21 @@ import { customElement } from 'lit/decorators.js';
 import './controls/player-controls';
 import './seekbar/seek-bar';
 import './volume-control/volume-control';
+import { designTokens } from '../../styles/tokens.css';
 
 @customElement('audio-player')
 export class AudioPlayer extends LitElement {
-  static override styles = css`
+  static override styles = [designTokens, css`
     .audio-player-container {
       display: flex;
       align-items: center;
-      gap: 0.5em;
+      gap: 8px;
     }
 
     .player-main {
       flex: 1;
     }
-  `;
+  `];
 
   override render() {
     return html`

frontend/src/components/audio-player/controls/player-controls.ts

@@ -4,6 +4,7 @@ import '@awesome.me/webawesome/dist/components/icon/icon.js';
 import { PlayerController } from '@store/controllers/player-controller';
 import { queueStore } from '@store/queue-store';
 import type { RepeatMode } from '@store/queue-store';
+import { designTokens } from '../../../styles/tokens.css';
 
 @customElement('player-controls')
 export class PlayerControls extends LitElement {
@@ -38,7 +39,7 @@ export class PlayerControls extends LitElement {
     this.unsubscribeQueue?.();
   }
 
-  static override styles = css`
+  static override styles = [designTokens, css`
     #player-control-buttons {
       display: flex;
       justify-content: center;
@@ -77,7 +78,7 @@ export class PlayerControls extends LitElement {
       bottom: 2px;
       right: 2px;
     }
-  `;
+  `];
 
   private handlePlayClick = () => {
     queueStore.play();

frontend/src/components/audio-player/seekbar/seek-bar.ts

@@ -4,6 +4,7 @@ import { ref, createRef } from 'lit/directives/ref.js';
 import WaSlider from '@awesome.me/webawesome/dist/components/slider/slider.js';
 import { formatSeconds } from '@utils/time';
 import { PlayerController } from '@store/controllers/player-controller';
+import { designTokens } from '../../../styles/tokens.css';
 
 const ProgressIntervalMillis = 1000;
 
@@ -17,16 +18,16 @@ export class SeekBar extends LitElement {
   @state()
   private seekValue: number = 0;
 
-  static override styles = css`
+  static override styles = [designTokens, css`
     wa-slider {
       --track-size: 6px;
       flex: 1;
-      margin: 0 1em;
+      margin: 0 16px;
       --wa-tooltip-background-color: var(--yj-bg-elevated, #343a40);
       --wa-tooltip-content-color: var(--yj-text-primary, white);
       --wa-tooltip-border-color: var(--yj-bg-elevated, #343a40);
       --wa-tooltip-border-radius: 4px;
-      --wa-tooltip-font-size: 0.875em;
+      --wa-tooltip-font-size: var(--yj-text-lg);
     }
 
     wa-slider::part(track) {
@@ -46,7 +47,7 @@ export class SeekBar extends LitElement {
       justify-content: space-between;
       align-items: center;
     }
-  `;
+  `];
 
   // ===================================================================
   // DERIVED STATE

frontend/src/components/audio-player/volume-control/volume-control.ts

@@ -4,6 +4,7 @@ import '@awesome.me/webawesome/dist/components/icon/icon.js';
 import '@awesome.me/webawesome/dist/components/slider/slider.js';
 import type WaSlider from '@awesome.me/webawesome/dist/components/slider/slider.js';
 import { PlayerController } from '@store/controllers/player-controller';
+import { designTokens } from '../../../styles/tokens.css';
 
 @customElement('volume-control')
 export class VolumeControl extends LitElement {
@@ -13,7 +14,7 @@ export class VolumeControl extends LitElement {
   @state()
   private showSlider = false;
 
-  static override styles = css`
+  static override styles = [designTokens, css`
     :host {
       position: relative;
       display: inline-flex;
@@ -25,7 +26,7 @@ export class VolumeControl extends LitElement {
       border: none;
       cursor: pointer;
       color: inherit;
-      padding: 0.25em;
+      padding: 4px;
       display: flex;
       align-items: center;
     }
@@ -38,8 +39,8 @@ export class VolumeControl extends LitElement {
       background: var(--yj-bg-surface, #1a1a1a);
       border: 1px solid var(--yj-border-subtle, #333);
       border-radius: 8px;
-      padding: 1em 0.5em;
-      margin-bottom: 0.5em;
+      padding: 16px 8px;
+      margin-bottom: 8px;
       display: flex;
       justify-content: center;
       z-index: 100;
@@ -47,8 +48,8 @@ export class VolumeControl extends LitElement {
 
     wa-slider {
       --track-size: 6px;
-      --thumb-width: 1em;
-      --thumb-height: 1em;
+      --thumb-width: 16px;
+      --thumb-height: 16px;
     }
 
     wa-slider::part(track) {
@@ -63,7 +64,7 @@ export class VolumeControl extends LitElement {
     wa-slider::part(thumb) {
       background: var(--yj-bg-base, black);
     }
-  `;
+  `];
 
   // ===================================================================
   // DERIVED STATE