fix(discord): add Apple Music cover opt-in, show Paused state

- iTunes Search API calls are now gated behind enableAppleMusicCoversDiscord
  (default: false). No external requests to Apple are made unless the user
  explicitly enables the new opt-in toggle in Settings.
- When the toggle is flipped, Discord presence is immediately re-sent for
  the current track (coversSettingChanged bypasses the early-return guard).
- When paused, activity type switches to Playing (no auto-timer) and state
  text shows "Paused" instead of the artist name.
- New authStore field + setter; new Settings toggle shown only when Discord
  RPC is enabled; i18n keys added to all 7 languages.

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

src/pages/Settings.tsx

@@ -637,6 +637,21 @@ export default function Settings() {
                   <span className="toggle-track" />
                 </label>
               </div>
+              {auth.discordRichPresence && (
+                <>
+                  <div className="settings-section-divider" />
+                  <div className="settings-toggle-row" style={{ paddingLeft: 16 }}>
+                    <div>
+                      <div style={{ fontWeight: 500 }}>{t('settings.discordAppleCovers')}</div>
+                      <div style={{ fontSize: 12, color: 'var(--text-muted)' }}>{t('settings.discordAppleCoversDesc')}</div>
+                    </div>
+                    <label className="toggle-switch" aria-label={t('settings.discordAppleCovers')}>
+                      <input type="checkbox" checked={auth.enableAppleMusicCoversDiscord} onChange={e => auth.setEnableAppleMusicCoversDiscord(e.target.checked)} />
+                      <span className="toggle-track" />
+                    </label>
+                  </div>
+                </>
+              )}
               <div className="settings-section-divider" />
               <div className="settings-toggle-row">
                 <div>