refactor: replace cyan accent with ember orange across entire frontend

Swap accent color from cyan (#22d3ee) to ember orange (#f97316) site-wide.
Cyan caused contrast issues and felt generic — orange brings warmth and
urgency fitting for a troubleshooting tool.

Changes:
- CSS variables: accent, accent-hover, accent-dim, accent-text, primary, ring
- Warning color shifted from amber (#fbbf24) to yellow (#eab308) for
  semantic separation from orange accent
- Brand SVGs: logo gradient updated to orange
- 50+ component files: all hardcoded cyan hex values, Tailwind cyan-*
  classes, and rgba(34,211,238,...) glow values replaced
- landing.css: all 45+ cyan references + 5 old border color fixes
- DESIGN-SYSTEM.md bumped to v5 with decisions log
- CLAUDE.md: all color references synced to charcoal palette + orange accent
- PWA theme-color meta tag updated to match sidebar (#10121a)

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

frontend/src/components/dashboard/PreparedSessions.tsx

@@ -31,9 +31,9 @@ export function PreparedSessions() {
     <div className="card-flat p-5 fade-in" style={{ animationDelay: '200ms' }}>
       <div className="flex items-center justify-between mb-3">
         <div className="flex items-center gap-2">
-          <ClipboardList className="h-4 w-4 text-cyan-400" />
+          <ClipboardList className="h-4 w-4 text-orange-400" />
           <h3 className="font-heading text-sm font-semibold text-foreground">Prepared for You</h3>
-          <span className="flex h-5 w-5 items-center justify-center rounded-full bg-cyan-400/20 text-[0.625rem] font-bold text-cyan-400">
+          <span className="flex h-5 w-5 items-center justify-center rounded-full bg-orange-400/20 text-[0.625rem] font-bold text-orange-400">
             {sessions.length}
           </span>
         </div>
@@ -52,7 +52,7 @@ export function PreparedSessions() {
               onClick={() => handleStart(session)}
               className={cn(
                 'group flex w-full items-center justify-between gap-3 rounded-lg border border-border px-4 py-3',
-                'text-left transition-all hover:border-cyan-500/30 hover:bg-cyan-500/5'
+                'text-left transition-all hover:border-orange-500/30 hover:bg-orange-500/5'
               )}
             >
               <div className="min-w-0 flex-1">