feat: dynamic PWA manifest with configurable name, description and icons

- Add app/manifest.ts to serve /manifest.webmanifest dynamically at runtime
- Name, short_name, description, theme_color and background_color are read
  from env vars (APP_NAME, APP_SHORT_NAME, APP_DESCRIPTION, PWA_THEME_COLOR,
  PWA_BACKGROUND_COLOR) with Bulwark defaults as fallback
- Add /api/pwa-icon/[size] route that auto-generates 192x192 and 512x512 PNG
  icons from PWA_ICON_URL (or FAVICON_URL as fallback) using Sharp; results
  are cached in memory
- Remove static manifest: '/manifest.json' from layout metadata; Next.js
  injects the link automatically from app/manifest.ts
- Fix pre-existing ESLint no-undef on RequestInit in browser-navigation.ts

app/api/pwa-icon/[size]/route.ts

@@ -0,0 +1,66 @@
+import { NextRequest, NextResponse } from 'next/server';
+import sharp from 'sharp';
+import path from 'node:path';
+import { readFile } from 'node:fs/promises';
+
+const VALID_SIZES = new Set([192, 512]);
+
+// Cache resized images in memory to avoid reprocessing on every request
+const cache = new Map<number, Blob>();
+
+async function fetchSourceImage(iconUrl: string): Promise<Buffer> {
+  // Absolute URL (http/https)
+  if (iconUrl.startsWith('http://') || iconUrl.startsWith('https://')) {
+    const res = await fetch(iconUrl);
+    if (!res.ok) throw new Error(`Failed to fetch PWA icon: ${res.status}`);
+    return Buffer.from(await res.arrayBuffer());
+  }
+
+  // Path relative to public/ directory
+  const publicPath = path.join(process.cwd(), 'public', iconUrl.replace(/^\//, ''));
+  return readFile(publicPath);
+}
+
+export async function GET(
+  _req: NextRequest,
+  { params }: { params: Promise<{ size: string }> }
+) {
+  const { size: sizeParam } = await params;
+  const size = parseInt(sizeParam, 10);
+
+  if (!VALID_SIZES.has(size)) {
+    return new NextResponse('Invalid size. Allowed: 192, 512', { status: 400 });
+  }
+
+  const iconUrl = process.env.PWA_ICON_URL || process.env.FAVICON_URL;
+  if (!iconUrl) {
+    return new NextResponse('No PWA icon configured', { status: 404 });
+  }
+
+  const pngHeaders = {
+    'Content-Type': 'image/png',
+    'Cache-Control': 'public, max-age=86400',
+  };
+
+  try {
+    if (cache.has(size)) {
+      return new NextResponse(cache.get(size)!, { headers: pngHeaders });
+    }
+
+    const sourceBuffer = await fetchSourceImage(iconUrl);
+    const resized = await sharp(sourceBuffer)
+      .resize(size, size, { fit: 'contain', background: { r: 0, g: 0, b: 0, alpha: 0 } })
+      .png()
+      .toBuffer();
+
+    const ab = new ArrayBuffer(resized.byteLength);
+    new Uint8Array(ab).set(resized);
+    const blob = new Blob([ab], { type: 'image/png' });
+    cache.set(size, blob);
+
+    return new NextResponse(blob, { headers: pngHeaders });
+  } catch (err) {
+    console.error('Failed to generate PWA icon:', err);
+    return new NextResponse('Failed to generate icon', { status: 500 });
+  }
+}