feat: add Windows PowerShell port (clash.ps1 + install.ps1)

- clash.ps1: 1:1 port of macOS clash script to PowerShell 7
  - TUN-only mode, auto UAC elevation via Start-Process -Verb RunAs
  - Subcommands: start/stop/restart/reload/status/link/open/edit/
    log/cleanup/doctor/verge-off/help + interactive menu
  - win_adapt_config: strip Linux-only fields, stack system→gvisor
  - wintun adapter + route cleanup for network recovery
  - ANSI colors (pwsh 7 + Windows Terminal)
  - 5-path mihomo binary detection (Get-Command→scoop→~/Mihomo→LOCALAPPDATA→ProgramFiles)

- install.ps1: one-command Windows deploy
  - Detect pwsh 7, download mihomo v1.19.15 + wintun.dll 0.14.1
  - Architecture-aware (amd64/arm64)
  - Deploy clash.ps1 to PATH

- README.md: add Windows section
- .gitignore: add wintun.dll, *.exe

.gitignore

@@ -4,11 +4,16 @@ config.yaml
 # 运行时数据
 *.pid
 *.log
+*.err.log
 cache.db
 
 # 代理节点缓存（含订阅链接和节点信息）
 proxy_provider/
 rules/
 
+# Windows
+wintun.dll
+*.exe
+
 # macOS 系统文件
 .DS_Store