f-21: refactor: add dispatcher layer for MQTT migration

Introduce internal/dispatcher package with a Command interface and typed
commands (CreateVPC, DeleteVPC, CreateSubnet, DeleteSubnet). The API
handlers now call dispatcher.Dispatch() instead of enqueuing closures
directly, decoupling transport (HTTP today, MQTT tomorrow) from execution.

Signed-off-by: GnomeZworc <nicolas.boufidjeline@g3e.fr>

internal/dispatcher/dispatcher.go

@@ -0,0 +1,29 @@
+package dispatcher
+
+import (
+	"log"
+
+	"git.g3e.fr/syonad/two/pkg/worker"
+	"github.com/dgraph-io/badger/v4"
+)
+
+type Command interface {
+	Execute(db *badger.DB) error
+}
+
+type Dispatcher struct {
+	queue *worker.Queue
+	db    *badger.DB
+}
+
+func New(queue *worker.Queue, db *badger.DB) *Dispatcher {
+	return &Dispatcher{queue: queue, db: db}
+}
+
+func (d *Dispatcher) Dispatch(cmd Command) {
+	d.queue.Submit(func() {
+		if err := cmd.Execute(d.db); err != nil {
+			log.Printf("command error (%T): %v", cmd, err)
+		}
+	})
+}