feat: per-theme accent + Activity WhatsApp(en)/GitHub cards, softer icon borders

- theme: store accent separately for light/dark (theme-core/controls)
- en contacts: WhatsApp card instead of VK (wa.me link)
- Activity: add GitHub card (logo webp) in both locales
- mp-card__image border uses --line to match card (less contrast)

src/partials/mini-projects-section.html

@@ -108,6 +108,36 @@
                 </div>
               </a>
             </li>
+            <li class="mini-projects-grid__item" data-mp-cells="2">
+              <a
+                class="mp-card mp-card--link mp-card--horizontal mp-card--hor-image"
+                href="https://github.com/mamadaevv"
+                target="_blank"
+                rel="noopener noreferrer"
+                aria-label="GitHub — открыть профиль"
+              >
+                <div class="mp-card__media" aria-hidden="true">
+                  <img
+                    class="mp-card__image"
+                    src="{{assetPrefix}}assets/misc/github_logo.webp"
+                    alt=""
+                    width="800"
+                    height="800"
+                    loading="lazy"
+                    decoding="async"
+                  />
+                </div>
+                <div class="mp-card__body">
+                  <h3 class="mp-card__title">
+                    GitHub
+                    <span class="mp-card__ext" aria-hidden="true"></span>
+                  </h3>
+                  <p class="mp-card__desc">
+                    Мои проекты и эксперименты с кодом.
+                  </p>
+                </div>
+              </a>
+            </li>
             <li class="mini-projects-grid__item" data-mp-cells="2">
               <a
                 class="mp-card mp-card--link mp-card--compact"