M3: theme-aware SVG architecture diagrams + hero motion

Hand-authored inline-SVG Diagram component (no runtime JS, CSP-clean,
themeable) rendering edge-AI, IaC-fleet and homelab architectures on the
case studies. Staggered CSS hero entrance, motion-aware.

src/pages/projects/[slug].astro

@@ -1,5 +1,6 @@
 ---
 import Layout from "../../layouts/Layout.astro";
+import Diagram from "../../components/Diagram.astro";
 import { getCollection, render } from "astro:content";
 import type { GetStaticPaths } from "astro";
 
@@ -40,6 +41,8 @@ const { Content } = await render(entry);
         )}
       </header>
 
+      {p.diagram && <Diagram name={p.diagram} />}
+
       <div class="prose case__body" data-reveal>
         <Content />
       </div>