feat(browser-ext): move browser extension to browser-ext/ and update API client to tRPC

- Create browser-ext/ with full extension code (MV3 manifest, background
  service worker, content script, popup, options page)
- Add tRPC API client that communicates with unified monolith endpoints
- Implement cache, settings, and phishing detection utilities
- Create extension tRPC router in web app (getAuthStatus, linkDevice,
  reportPhishing)
- Configure Vite build with manifest V3 support
- Write unit tests for cache, phishing detector, and API client
- All 20 tests passing, TypeScript lint clean

browser-ext/scripts/generate-icons.mjs

@@ -0,0 +1,80 @@
+import { writeFileSync, mkdirSync } from "fs";
+import { resolve } from "path";
+import { deflateSync } from "zlib";
+
+const __dirname = import.meta.dirname;
+const iconsDir = resolve(__dirname, "../public/icons");
+mkdirSync(iconsDir, { recursive: true });
+
+function crc32(buf) {
+  let crc = 0xffffffff;
+  const table = new Int32Array(256);
+  for (let i = 0; i < 256; i++) {
+    let c = i;
+    for (let j = 0; j < 8; j++) c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1;
+    table[i] = c;
+  }
+  for (let i = 0; i < buf.length; i++) crc = table[(crc ^ buf[i]) & 0xff] ^ (crc >>> 8);
+  return (crc ^ 0xffffffff) >>> 0;
+}
+
+function chunk(type, data) {
+  const len = Buffer.alloc(4);
+  len.writeUInt32BE(data.length);
+  const typeB = Buffer.from(type, "ascii");
+  const crcData = Buffer.concat([typeB, data]);
+  const crcV = Buffer.alloc(4);
+  crcV.writeUInt32BE(crc32(crcData));
+  return Buffer.concat([len, typeB, data, crcV]);
+}
+
+function createPNG(size) {
+  const raw = Buffer.alloc(size * size * 4);
+  const cx = size / 2;
+  const cy = size / 2;
+  const r = size * 0.42;
+
+  for (let y = 0; y < size; y++) {
+    for (let x = 0; x < size; x++) {
+      const dx = x - cx;
+      const dy = y - cy;
+      const dist = Math.sqrt(dx * dx + dy * dy);
+      const i = (y * size + x) * 4;
+      if (dist <= r) {
+        raw[i] = 99;
+        raw[i + 1] = 102;
+        raw[i + 2] = 241;
+        raw[i + 3] = 255;
+      } else {
+        raw[i] = 0;
+        raw[i + 1] = 0;
+        raw[i + 2] = 0;
+        raw[i + 3] = 0;
+      }
+    }
+  }
+
+  const filter = Buffer.alloc(size * size + size);
+  for (let y = 0; y < size; y++) {
+    filter[y * (size * 4 + 1)] = 0;
+    raw.copy(filter, y * (size * 4 + 1) + 1, y * size * 4, (y + 1) * size * 4);
+  }
+
+  const compressed = deflateSync(filter);
+  const ihdr = Buffer.alloc(13);
+  ihdr.writeUInt32BE(size, 0);
+  ihdr.writeUInt32BE(size, 4);
+  ihdr[8] = 8;
+  ihdr[9] = 6;
+  ihdr[10] = 0;
+  ihdr[11] = 0;
+  ihdr[12] = 0;
+
+  const sig = Buffer.from([137, 80, 78, 71, 13, 10, 26, 10]);
+  return Buffer.concat([sig, chunk("IHDR", ihdr), chunk("IDAT", compressed), chunk("IEND", Buffer.alloc(0))]);
+}
+
+for (const size of [16, 48, 128]) {
+  writeFileSync(resolve(iconsDir, `icon-${size}.png`), createPNG(size));
+  console.log(`Created icon-${size}.png`);
+}