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/tree-editor/GlowEdge.tsx

@@ -54,14 +54,14 @@ export function GlowEdgeDefs() {
 
         {/* Downstream: cyan brand */}
         <linearGradient id="edge-gradient-downstream" x1="0%" y1="0%" x2="0%" y2="100%">
-          <stop offset="0%" stopColor="#06b6d4" />
-          <stop offset="100%" stopColor="#22d3ee" />
+          <stop offset="0%" stopColor="#ea580c" />
+          <stop offset="100%" stopColor="#f97316" />
         </linearGradient>
 
         {/* Upstream: amber */}
         <linearGradient id="edge-gradient-upstream" x1="0%" y1="100%" x2="0%" y2="0%">
           <stop offset="0%" stopColor="#f59e0b" />
-          <stop offset="100%" stopColor="#fbbf24" />
+          <stop offset="100%" stopColor="#eab308" />
         </linearGradient>
 
         {/* Glow filters */}