perf: fix PageSpeed Insights issues (WebGL errors, bfcache, redirects, a11y)

- Add WebGL support detection in ShaderGradientBackground to prevent console errors
- Add .catch() fallback to ShaderGradientBackground dynamic import
- Remove hardcoded aria-label from consent banner minimize button (fixes label-content-name-mismatch)
- Use rewrite instead of redirect for root locale routing (eliminates one redirect hop)
- Change n8n API cache headers from no-store to no-cache (enables bfcache)
- Add three and @react-three/fiber to optimizePackageImports for better tree-shaking

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

app/components/ClientProviders.tsx

@@ -15,7 +15,7 @@ const BackgroundBlobs = dynamic(() => import("@/components/BackgroundBlobs").cat
 });
 
 const ShaderGradientBackground = dynamic(
-  () => import("./ShaderGradientBackground"),
+  () => import("./ShaderGradientBackground").catch(() => ({ default: () => null })),
   { ssr: false, loading: () => null }
 );
 

app/components/ConsentBanner.tsx

@@ -54,8 +54,6 @@ export default function ConsentBanner() {
             type="button"
             onClick={() => setMinimized(true)}
             className="shrink-0 text-xs text-stone-500 hover:text-stone-900 transition-colors"
-            aria-label="Minimize privacy banner"
-            title="Minimize"
           >
             {s.hide}
           </button>

app/components/ShaderGradientBackground.tsx

@@ -1,9 +1,23 @@
 "use client";
 
-import React from "react";
+import React, { useEffect, useState } from "react";
 import { ShaderGradientCanvas, ShaderGradient } from "@shadergradient/react";
 
 const ShaderGradientBackground = () => {
+  const [supported, setSupported] = useState(true);
+
+  useEffect(() => {
+    try {
+      const canvas = document.createElement("canvas");
+      const gl = canvas.getContext("webgl") || canvas.getContext("experimental-webgl");
+      if (!gl) setSupported(false);
+    } catch {
+      setSupported(false);
+    }
+  }, []);
+
+  if (!supported) return null;
+
   return (
     <div
       style={{