feat: replace hardcoded orange hex values with blue equivalents

BrandLogo gradient, EmptyStateIllustrations SVGs, categoryColors,
landing page, brand SVG assets, and all remaining files.
Warning #eab308 → #fbbf24 (amber). categoryColors deduped.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/assets/brand/icon.svg

@@ -1,8 +1,8 @@
 <svg viewBox="0 0 80 80" fill="none" xmlns="http://www.w3.org/2000/svg">
   <defs>
     <linearGradient id="resolutionflow-gradient" x1="0%" y1="0%" x2="100%" y2="0%">
-      <stop offset="0%" stop-color="#ea580c"/>
-      <stop offset="100%" stop-color="#f97316"/>
+      <stop offset="0%" stop-color="#3b82f6"/>
+      <stop offset="100%" stop-color="#60a5fa"/>
     </linearGradient>
   </defs>
   <!-- Input circles (choices) -->

frontend/src/assets/brand/logo-horizontal.svg

@@ -1,8 +1,8 @@
 <svg viewBox="0 0 320 80" fill="none" xmlns="http://www.w3.org/2000/svg">
   <defs>
     <linearGradient id="rf-gradient" x1="0%" y1="0%" x2="100%" y2="0%">
-      <stop offset="0%" stop-color="#ea580c"/>
-      <stop offset="100%" stop-color="#f97316"/>
+      <stop offset="0%" stop-color="#3b82f6"/>
+      <stop offset="100%" stop-color="#60a5fa"/>
     </linearGradient>
   </defs>
   

frontend/src/assets/brand/logo-with-tagline.svg

@@ -1,8 +1,8 @@
 <svg viewBox="0 0 320 100" fill="none" xmlns="http://www.w3.org/2000/svg">
   <defs>
     <linearGradient id="rf-gradient-tag" x1="0%" y1="0%" x2="100%" y2="0%">
-      <stop offset="0%" stop-color="#ea580c"/>
-      <stop offset="100%" stop-color="#f97316"/>
+      <stop offset="0%" stop-color="#3b82f6"/>
+      <stop offset="100%" stop-color="#60a5fa"/>
     </linearGradient>
   </defs>