style(brand): unify orange to #FA7850 + yellow token; fix tablet header gap

- Brand orange is now the official #FA7850 everywhere: folded the stray
  oranges (#F2762E, #E8833A, #ff6b2c) into it and kept a single darker shade
  (#E85D2A) for gradient depth + button hover. Added the official brand
  --yellow (#FFE16E) token.
- Tablet header gap (769-1024px): the fixed header shrinks 80->60px there but
  first-section paddings kept their 80px clearance; pull the first section up
  by the 20px delta in that range only (phones untouched). Verified on
  interior pages and the full-bleed homepage hero — gap now matches desktop,
  no overlap.
- Re-stamped cache-bust (v=f95de694).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

css/components/_buttons.css

@@ -52,7 +52,7 @@
     font-size: 18px;
     line-height: 28px;
 }
-.btn-primary-orange:hover { background: #E8663F; }
+.btn-primary-orange:hover { background: #E85D2A; }
 
 .btn-secondary {
     background-color: #FFFFFF;