feat: application icon for Windows taskbar + exe

- scripts/gen_icon.py: generates 256x256 SSH client icon (dark terminal
  window with >_ prompt and SSH connection nodes), outputs multi-size
  ICO (16-256px) + PNG
- resources/icon.ico + icon.png: generated icon files
- main.py: _get_icon_path() searches _MEIPASS (onefile), exe dir, source
  dir; sets app + window icon
- build.spec: bundles icon files via datas=, sets exe icon=icon.ico
- Windows taskbar will now show the custom icon instead of default PyInstaller icon

main.py

@@ -20,11 +20,35 @@ _setup_path()
 
 from PyQt5.QtWidgets import QApplication
 from PyQt5.QtCore import Qt
-from PyQt5.QtGui import QFont
+from PyQt5.QtGui import QFont, QIcon, QPixmap
 
 from ui.main_window import MainWindow, APP_NAME
 
 
+def _get_icon_path() -> str:
+    """找到 icon.ico / icon.png 的路径"""
+    # 搜索目录列表：源码运行 / PyInstaller onefile / PyInstaller onedir
+    search_dirs = []
+    if getattr(sys, "frozen", False):
+        # PyInstaller onefile: 资源解压到 _MEIPASS
+        meipass = getattr(sys, "_MEIPASS", None)
+        if meipass:
+            search_dirs.append(Path(meipass))
+            search_dirs.append(Path(meipass) / "resources")
+        # exe 同目录（onedir 模式或用户手动放）
+        search_dirs.append(Path(sys.executable).parent)
+        search_dirs.append(Path(sys.executable).parent / "resources")
+    else:
+        search_dirs.append(Path(__file__).parent)
+        search_dirs.append(Path(__file__).parent / "resources")
+    for d in search_dirs:
+        for name in ("icon.png", "icon.ico"):
+            p = d / name
+            if p.exists():
+                return str(p)
+    return ""
+
+
 def main():
     # Windows 上高 DPI 适配
     if hasattr(Qt, "AA_EnableHighDpiScaling"):
@@ -39,7 +63,14 @@ def main():
     f = QFont("Consolas", 10)
     app.setFont(f)
 
+    # 设置应用图标（任务栏 + 窗口标题栏）
+    icon_path = _get_icon_path()
+    if icon_path:
+        app.setWindowIcon(QIcon(icon_path))
+
     w = MainWindow()
+    if icon_path:
+        w.setWindowIcon(QIcon(icon_path))
     w.show()
     sys.exit(app.exec_())