refactor: rename CLI binary from lab to labctl

Updated everywhere: constants, package.json bin, completions,
nfpm packaging, build scripts, CI, banner text. Binary is now
/usr/bin/labctl. Internal package names (@lab/*) unchanged.

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

bastion/nfpm.yaml

@@ -1,4 +1,4 @@
-name: lab
+name: labctl
 arch: amd64
 version: 0.1.0
 release: "1"
@@ -6,15 +6,15 @@ maintainer: michal
 description: Lab infrastructure CLI for bare-metal provisioning
 license: MIT
 contents:
-  - src: ./dist/lab
-    dst: /usr/bin/lab
+  - src: ./dist/labctl
+    dst: /usr/bin/labctl
     file_info:
       mode: 0755
-  - src: ./completions/lab.bash
-    dst: /usr/share/bash-completion/completions/lab
+  - src: ./completions/labctl.bash
+    dst: /usr/share/bash-completion/completions/labctl
     file_info:
       mode: 0644
-  - src: ./completions/lab.fish
-    dst: /usr/share/fish/vendor_completions.d/lab.fish
+  - src: ./completions/labctl.fish
+    dst: /usr/share/fish/vendor_completions.d/labctl.fish
     file_info:
       mode: 0644