FEAT: icon exe = favicon cua app — favicon.svg -> PNG -> ICO (6 sizes 16-128)

- engine.spec: icon='src-tauri/icons/favicon.ico' (cung nguon voi icon hien thi trong app, truoc day dung icon.ico mac dinh khac favicon)
- tools/gen_favicon_ico.js: script tai sinh ICO tu app/templates/favicon.svg (resvg-js WASM, khong can libcairo)
- Verify: ICO 6 sizes (16/24/32/48/64/128), 571 mau, binary chay OK

engine.spec

@@ -124,5 +124,7 @@ exe = EXE(
     upx_exclude=[],
     runtime_tmpdir=None,
     console=False,  # True khi debug (xem log truc tiep), False cho production
-    icon='src-tauri/icons/icon.ico',
+    # Icon exe = favicon cua app (app/templates/favicon.svg -> render PNG -> ICO,
+    # sinh boi tools/gen_favicon_ico.py). Cung nguon voi icon hien thi trong app.
+    icon='src-tauri/icons/favicon.ico',
 )

tools/gen_favicon_ico.js

@@ -0,0 +1,55 @@
+// Sinh src-tauri/icons/favicon.ico tu app/templates/favicon.svg (icon exe).
+// Dung: node tools/gen_favicon_ico.js
+// (Can @resvg/resvg-js — npm install @resvg/resvg-js trong thu muc lam viec,
+// hoac chay trong thu muc da cai. Output: src-tauri/icons/favicon.ico.)
+// ICO chua cac size 16/24/32/48/64/128 — Windows dung cho exe icon.
+const fs = require('fs');
+const path = require('path');
+
+const ROOT = path.resolve(__dirname, '..');
+const SVG = path.join(ROOT, 'app', 'templates', 'favicon.svg');
+const OUT = path.join(ROOT, 'src-tauri', 'icons', 'favicon.ico');
+
+let Resvg;
+try {
+  ({ Resvg } = require('@resvg/resvg-js'));
+} catch (e) {
+  console.error('Thieu @resvg/resvg-js. Chay: npm install @resvg/resvg-js');
+  process.exit(1);
+}
+
+const svg = fs.readFileSync(SVG, 'utf8');
+const SIZES = [16, 24, 32, 48, 64, 128];
+
+function buildIco(images) {
+  const header = Buffer.alloc(6);
+  header.writeUInt16LE(0, 0);
+  header.writeUInt16LE(1, 2);
+  header.writeUInt16LE(images.length, 4);
+  const entries = [];
+  const datas = [];
+  let offset = 6 + 16 * images.length;
+  for (const { size, data } of images) {
+    const entry = Buffer.alloc(16);
+    const dim = size >= 256 ? 0 : size;
+    entry.writeUInt8(dim, 0);
+    entry.writeUInt8(dim, 1);
+    entry.writeUInt8(0, 2);
+    entry.writeUInt8(0, 3);
+    entry.writeUInt16LE(1, 4);
+    entry.writeUInt16LE(32, 6);
+    entry.writeUInt32LE(data.length, 8);
+    entry.writeUInt32LE(offset, 12);
+    entries.push(entry);
+    datas.push(data);
+    offset += data.length;
+  }
+  return Buffer.concat([header, ...entries, ...datas]);
+}
+
+const pngs = SIZES.map(s => ({
+  size: s,
+  data: new Resvg(svg, { fitTo: { mode: 'width', value: s }, background: 'rgba(0,0,0,0)' }).render().asPng(),
+}));
+fs.writeFileSync(OUT, buildIco(pngs));
+console.log('favicon.ico ->', OUT, fs.statSync(OUT).size, 'bytes');