Fix dogfood QA: 404, content hygiene, grid UX, a11y, CTAs

- Add branded NotFound catch-all (no more blank unknown routes)
- Portfolio cards: shimmer skeleton, eager first-row thumbs, real alts
- Hide empty categories; rename CAD view slug to avoid collision
- Resume summary preserves paragraphs/bullets
- Home/About/footer hire contact mailto CTA
- Sticky header scroll-padding; chip aria-labels
- Security headers; Flickr import strip View On Black + junk tags
- Content cleanup script for grammar, residue, tags, featured

client/src/components/ProjectCard.scss

@@ -27,11 +27,34 @@
     overflow: hidden;
     background: #0e0e10;
 
+    &.is-loading::before {
+      content: "";
+      position: absolute;
+      inset: 0;
+      background: linear-gradient(
+        110deg,
+        #141416 0%,
+        #1c1c20 40%,
+        #141416 60%,
+        #0e0e10 100%
+      );
+      background-size: 200% 100%;
+      animation: project-card-shimmer 1.25s ease-in-out infinite;
+      z-index: 0;
+    }
+
     img {
+      position: relative;
+      z-index: 1;
       width: 100%;
       height: 100%;
       object-fit: cover;
-      transition: transform 0.55s ease;
+      opacity: 0;
+      transition: transform 0.55s ease, opacity 0.35s ease;
+
+      &.is-loaded {
+        opacity: 1;
+      }
     }
   }
 
@@ -93,3 +116,12 @@
   grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
   gap: 1.35rem;
 }
+
+@keyframes project-card-shimmer {
+  0% {
+    background-position: 100% 0;
+  }
+  100% {
+    background-position: -100% 0;
+  }
+}