feat(server): randomize the seeded admin initial password (#172)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

install.ps1

@@ -442,5 +442,5 @@ if ($PathUpdateMessage) {
 Write-Host ""
 Write-Host "Get started:"
 Write-Host "  penguin --help    # all commands"
-Write-Host "  penguin web       # start the Web UI at http://127.0.0.1:7364 (initial login: admin / penguin-2026)"
+Write-Host "  penguin web       # start the Web UI at http://127.0.0.1:7364 (login: admin, initial password printed on first start)"
 Write-Host "  penguin server    # headless server (PORT / HOST to override)"