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/pages/ResumePage.scss

@@ -55,6 +55,18 @@
     padding-left: 1rem;
     color: var(--text-muted);
     margin: 0 0 2rem;
+
+    p {
+      margin: 0 0 0.65rem;
+
+      &:last-child {
+        margin-bottom: 0;
+      }
+    }
+  }
+
+  &__summary-bullet {
+    padding-left: 0.15rem;
   }
 
   &__section {