fix: highlight active news filter button with primary colour

[Copilot]

The active filter button on the news page had no visible highlight — the selected item (e.g. 全部) appeared dimmer than inactive buttons rather than standing out.

Root cause: Nuxt UI v4 + Tailwind CSS v4 requires colour scales to be registered via @theme using --color-primary-* custom properties. The previous config passed a raw hex to ui.colors.primary, which is not a valid colour scale name — color="primary" had nothing to resolve and fell back silently.

Changes

• main.css — Add @theme block registering the full --color-primary-{50…950} scale using the existing Twinkle AI brand yellow (#ffd500):

  @theme {
    --color-primary-500: #ffd500; /* brand base */
    /* … full scale 50–950 */
  }

• app.config.ts — Replace primary: '#ffd500' with primary: 'primary' to reference the registered theme scale; rename legacy gray key to neutral (Nuxt UI v4 field name):

  colors: {
    primary: 'primary',
    neutral: 'zinc',
  }

• news.vue — Switch active filter button from variant="solid" to variant="outline" so the selection is communicated via primary-coloured border + text rather than a filled background, per the issue request for highlighted text:

  :variant="activeFilter === filter.value ? 'outline' : 'ghost'"
  :color="activeFilter === filter.value ? 'primary' : 'white'"

Original prompt

---

This section details on the original issue you should resolve

<issue_title>被選取導覽列按鈕沒有高亮</issue_title>
<issue_description>

在新聞頁面，被選取的頁面之導覽列沒有高亮顯示，這樣在 UX 體驗上面可能不清楚，提議是否可以高亮的文字採用官網的主要色系（primary color）？</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes 被選取導覽列按鈕沒有高亮 #41

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	twinkle-website	d2a91f2	Commit Preview URL Branch Preview URL	Feb 23 2026, 02:41 AM