feat: replace all hardcoded orange rgba with blue rgba

Mechanical find-and-replace: rgba(249,115,22,...) → rgba(96,165,250,...)
across ~40 component and page files.

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

frontend/src/components/layout/Sidebar.tsx

@@ -288,7 +288,7 @@ export function Sidebar() {
             'group relative flex items-center gap-3 rounded-lg px-3 py-2 text-[0.8125rem] font-medium transition-all duration-150',
             active
               ? isParentDimmed
-                ? 'bg-[rgba(249,115,22,0.05)] text-foreground/70'
+                ? 'bg-[rgba(96,165,250,0.05)] text-foreground/70'
                 : 'bg-accent-dim text-foreground'
               : 'text-muted-foreground hover:bg-input hover:text-foreground'
           )}