Upgrade Next.js to 15, fix first-load theme bug, add SVG assets

- Upgrade next 14.1.0 → 15.5.9, next-themes 0.2.1 → 0.4.6
- Fix theme not initializing on first load after server restart
- Add SVG logos and favicon, update site-logo to use SVGs
- Create shared Header component with skip-to-main link
- Add portfolio links to bento grid cards
- Improve accessibility: aria-describedby, prefers-reduced-motion
- Fix useFormState → useActionState for React 19 compatibility
- Fix founder-signature icon (use square favicon instead of wide logo)

apps/web/src/app/globals.css

@@ -87,7 +87,7 @@
     overflow: hidden;
     transition: all 300ms;
   }
-  
+
   .section-container {
     @apply mask-backdrop rounded-[2.5rem] p-12 md:p-20 text-card-foreground;
   }
@@ -95,8 +95,20 @@
   .glass-card {
     @apply mask-backdrop rounded-[2rem] p-10 text-card-foreground;
   }
-  
+
   .glass-card:hover {
     border-color: hsl(var(--primary) / 0.3);
   }
 }
+
+/* Respect users who prefer reduced motion */
+@media (prefers-reduced-motion: reduce) {
+  *,
+  *::before,
+  *::after {
+    animation-duration: 0.01ms !important;
+    animation-iteration-count: 1 !important;
+    transition-duration: 0.01ms !important;
+    scroll-behavior: auto !important;
+  }
+}