step 10: plugins system (Lua + templates) + DokuWiki as optional plugin

Plugin Manager:
- Discover plugins from .verstak/plugins/<name>/plugin.json
- Enable/disable per plugin
- Template definitions (JSON) → pre-filled node trees
- SQL migrations from plugins
- Built-in templates loaded from internal/core/plugins/builtin/templates/

Lua Runtime:
- Stub (gopher-lua placeholder) — ready for real implementation
- When dep added: hooks (on_init, on_vault_open, on_node_create),
  sandbox (no io/os.execute), Plugin API

GUI:
- Template selector in create node modal
- POST /api/nodes/from-template creates tree from template
- Built-in "Клиент" template: Overview note + Документы/Переписка/Скриншоты

CLI:
- verstak plugin list/enable/disable/templates

DokuWiki Importer:
- Moved to contrib/plugins/importer-dokuwiki/ (optional plugin)
- plugin.json + migration + README

DokuWiki removed from MVP core — now an opt-in plugin.

Acceptance: go build ./... pass, go test ./... pass (all packages).

cmd/verstak/main.go

@@ -8,6 +8,7 @@ import (
 	"strings"
 
 	"verstak/internal/core/actions"
+	"verstak/internal/core/plugins"
 	"verstak/internal/core/search"
 	"verstak/internal/core/storage"
 	"verstak/internal/core/vault"
@@ -37,6 +38,8 @@ func main() {
 		runLog(os.Args[2:])
 	case "index":
 		runIndex(os.Args[2:])
+	case "plugin":
+		runPlugin(os.Args[2:])
 	default:
 		fmt.Fprintf(os.Stderr, "Unknown command: %s\n", os.Args[1])
 		os.Exit(1)
@@ -593,3 +596,71 @@ func runIndexRebuild(args []string) {
 
 	fmt.Printf("indexed %d nodes\n", count)
 }
+
+// --- plugin ---
+
+func runPlugin(args []string) {
+	vaultPath, _ := stringFlag(args, "--vault")
+
+	if len(args) == 0 || args[0] == "--help" || args[0] == "-h" {
+		fmt.Println("verstak plugin — manage plugins")
+		fmt.Println()
+		fmt.Println("Usage: verstak plugin <command> [options]")
+		fmt.Println()
+		fmt.Println("Commands:")
+		fmt.Println("  list               List discovered plugins")
+		fmt.Println("  enable NAME        Enable a plugin")
+		fmt.Println("  disable NAME       Disable a plugin")
+		fmt.Println("  templates          List available templates")
+		os.Exit(0)
+	}
+
+	abs, _ := filepath.Abs(vaultPath)
+
+	switch args[0] {
+	case "list":
+		mgr := plugins.NewManager(abs)
+		mgr.Discover()
+		pp := mgr.Plugins()
+		if len(pp) == 0 {
+			fmt.Println("No plugins found.")
+			fmt.Println("Put plugins in .verstak/plugins/<name>/plugin.json")
+			return
+		}
+		for _, p := range pp {
+			status := "on"
+			if !p.Active {
+				status = "off"
+			}
+			fmt.Printf("%-20s %-6s %s\n", p.Meta.Name, status, p.Meta.Description)
+		}
+	case "enable", "disable":
+		if len(args) < 2 {
+			fmt.Fprintln(os.Stderr, "Error: plugin name required")
+			os.Exit(1)
+		}
+		mgr := plugins.NewManager(abs)
+		mgr.Discover()
+		name := args[1]
+		if args[0] == "enable" {
+			mgr.Enable(name)
+		} else {
+			mgr.Disable(name)
+		}
+		fmt.Printf("%s %s\n", args[0]+"d", name)
+	case "templates":
+		mgr := plugins.NewManager(abs)
+		mgr.Discover()
+		tmpls := mgr.Templates()
+		if len(tmpls) == 0 {
+			fmt.Println("No templates found.")
+			return
+		}
+		for _, t := range tmpls {
+			fmt.Printf("%-20s %-10s %s\n", t.Name, fmt.Sprintf("[%s]", t.Plugin), t.Description)
+		}
+	default:
+		fmt.Fprintf(os.Stderr, "Unknown plugin command: %s\n", args[0])
+		os.Exit(1)
+	}
+}