Error Feedback Service + friendly error handling across all pages

- Error Feedback Service: POST /api/feedback saves to JSONL, GET with admin token
- ErrorFeedback component: warm amber tones, friendly messages, 'Report Issue' button
- Replaced ALL red-themed error displays across 15+ pages with ErrorFeedback
- Kind classification: network, auth, location, upgrade, default messages
- QA test suite v2: 8-layer testing (system, API, render, scenario, edge, mobile, perf, security)
- Browser-based visual QA with Playwright (Layer 9)

src/app/nur/page.tsx

@@ -2,6 +2,7 @@
 
 import { useState, useEffect, useRef, Suspense, useCallback } from "react";
 import { useAuth } from "@/lib/AuthContext";
+import ErrorFeedback from "@/components/ErrorFeedback";
 import { PERSONAS, getPersona } from "@/lib/personas";
 import Link from "next/link";
 import { useRouter } from "next/navigation";
@@ -339,16 +340,18 @@ function NurChat() {
 
       {/* ── Error Message ── */}
       {error && (
-        <div className="mx-4 mb-2 flex items-start gap-2 bg-red-900/20 border border-red-800/30 rounded-xl px-3 py-2.5">
-          <AlertTriangle size={14} className="text-red-400 shrink-0 mt-0.5" />
-          <p className="text-xs text-red-300 flex-1">{error}</p>
-          <button
-            onClick={() => setError(null)}
-            className="text-red-400 hover:text-red-300 text-xs"
-          >
-            ✕
-          </button>
-        </div>
+        <ErrorFeedback
+          error={error}
+          kind={
+            error.includes("Upgrade") || error.includes("upgrade") || error.includes("premium")
+              ? "upgrade"
+              : error.includes("Network") || error.includes("network")
+              ? "network"
+              : "default"
+          }
+          onRetry={() => setError(null)}
+          context="Nur AI chat"
+        />
       )}
 
       {/* ── Input Area ── */}