feat: 添加 Justfile 简化常用命令，安装 just

Justfile

@@ -0,0 +1,35 @@
+# List all commands
+default:
+    @just --list
+
+# Rebuild current macOS host (auto-detect from hostname)
+[macos]
+darwin:
+    #!/usr/bin/env bash
+    attr=$(scutil --get LocalHostName | tr '[:upper:]' '[:lower:]' | sed 's/awesome-//')
+    sudo darwin-rebuild switch --flake .#"$attr"
+
+# Rebuild WSL host
+[linux]
+nixos:
+    sudo nixos-rebuild switch --flake .#wsl
+
+# Update all flake inputs
+update:
+    nix flake update
+
+# Edit encrypted secrets
+secrets:
+    sops secrets/secrets.yaml
+
+# Garbage-collect old generations
+gc:
+    nix-collect-garbage -d
+
+# Show flake outputs
+show:
+    nix flake show
+
+# Check flake for errors
+check:
+    nix flake check --no-build