slice 4: accent palette refinement — blue → teal

Replace the four accent-family hex codes site-wide with the teal palette
(keeps the dark theme; only swaps the accent family, not the dark base):

  #3b82f6 (accent primary CTA)   → #5B7C8D  (teal)        [839×]
  #2563eb (accent-dark / hover)  → #4A6473  (darker teal) [44×]
  #60a5fa (info link, lighter)   → #8FB0C3  (mid teal)    [68×]
  #1e3a5f (accent-muted bg)      → #2F4F5F  (navy)        [44×]

tailwind.config.js tokens updated to match (accent/accent-dark/accent-muted).
Sweep also covers tailwind.css. 108 files touched. The dark base (#0d0d0d,
#111, #161616, #1a1a1a etc.) is intentionally untouched.

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

src/app/api/newsletter/templates/route.ts

@@ -38,7 +38,7 @@ export async function POST(req: NextRequest) {
       subject_prefix: subject_prefix || '',
       header_text: header_text || '',
       footer_text: footer_text || '',
-      accent_color: accent_color || '#3b82f6',
+      accent_color: accent_color || '#5B7C8D',
       article_blocks: article_blocks || [],
       is_preset: false,
     })