fix: tfcode web fails after npm install — copy app dist in postinstall

The web command crashed because postinstall scripts never copied the
app/dist directory from the platform package. Added copyAppDir() to
both postinstall scripts, multi-path resolution in findAppDir() and
server static serving, and updated branding to use local favicon.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/tfcode/script/build-tfcode.ts

@@ -164,6 +164,10 @@ for (const item of targets) {
   }
 
   await $`rm -rf ./dist/${name}/bin/tui`
+  const appDistDir = path.resolve(dir, "../app/dist")
+  if (fs.existsSync(appDistDir)) {
+    fs.cpSync(appDistDir, path.join(dir, "dist", name, "bin", "app", "dist"), { recursive: true })
+  }
   await Bun.file(`dist/${name}/package.json`).write(
     JSON.stringify(
       {