feat: add worktree:scan CLI command and dashboard button

[ropi-bc]

Summary

• Adds a lerd worktree:scan CLI command that manually triggers a full worktree rescan across all registered sites — detects worktrees, ensures dependencies (vendor/, node_modules/, .env), mounts paths in podman, generates nginx vhosts, and reloads nginx
• Adds a POST /api/worktrees/scan API endpoint in the UI server
• Adds a "Scan Worktrees" button to the Watcher panel in the dashboard, styled with the existing git-worktree violet color scheme
• Extracts the shared cli.ScanWorktrees() function from the private scanWorktrees() in the watch daemon, eliminating duplication
• Refactors worktree vhost generation to accept config.Site instead of individual strings, enabling proper proxy and public dir detection for worktrees via a new worktreeVhostData() helper

Why

The file watcher detects new git worktrees automatically via fsnotify + 30s polling, but there was no way to manually trigger a full rescan. This is needed when:

• Worktrees were created while the watcher was not running
• Nginx vhosts need to be refreshed after configuration changes
• Debugging worktree setup issues

CLI usage

lerd worktree:scan
# Worktree vhost: feature-branch -> feature-branch.myapp.test
# Generated 3 worktree vhost(s) and reloaded nginx.

Test plan

• Run lerd worktree:scan with existing worktrees — verify vhosts are generated and nginx reloads
• Run lerd worktree:scan with no worktrees — verify "No worktree vhosts to generate." message
• Open the dashboard → System → Watcher panel → click "Scan Worktrees" button — verify it shows spinner, completes, and the sites list refreshes
• Verify the watcher daemon startup still works (the delegated scanWorktrees() path)
• Verify worktree vhosts now correctly detect proxy config and public dir from the parent site

🤖 Generated with Claude Code

[ropi-bc]

sorry, I was too eager to open the PR, and I see some issues with it. converted to draft and will reopen soon

[geodro]

Hey, thanks for taking your time! Can you update your commit message and PR and remove "Generated with Claude Code" ?