Fix missing H1 on list-style pages via SectionHeading template

SectionHeading always rendered its title as <h2>, so every page whose
only heading came from a shared section component (services hub,
promotions, cases, faq, contact, reviews, blog list) had no <h1> at
all. Add a level prop (default h2) and pass headingLevel="h1" from
each page where that section is the page's own top-level heading.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013otXCiTZsxdZ4SJKZ9wUky

public-site/components/sections/Promotions.jsx

@@ -3,7 +3,7 @@ import { ArrowUpRight } from 'lucide-react';
 import Reveal from '../Reveal.jsx';
 import SectionHeading from '../SectionHeading.jsx';
 
-export default function Promotions({ promotions, limit, moreHref, showMailNote = false }) {
+export default function Promotions({ promotions, limit, moreHref, showMailNote = false, headingLevel = 'h2' }) {
   if (promotions.length === 0) return null;
   const list = limit ? promotions.slice(0, limit) : promotions;
 
@@ -14,6 +14,7 @@ export default function Promotions({ promotions, limit, moreHref, showMailNote =
           eyebrow="promotions --active"
           title="Акции и специальные предложения"
           desc="Актуальные сроки и условия уточняйте у менеджера при обращении."
+          level={headingLevel}
         />
         <div className="grid sm:grid-cols-2 lg:grid-cols-3 gap-5">
           {list.map((p, i) => (