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/vpc_commands.go

@@ -0,0 +1,35 @@
+package dispatcher
+
+import (
+	"git.g3e.fr/syonad/two/internal/vpc"
+	"git.g3e.fr/syonad/two/pkg/db/kv"
+	"github.com/dgraph-io/badger/v4"
+)
+
+type CreateVPCCommand struct {
+	Name string
+}
+
+func (c CreateVPCCommand) Execute(db *badger.DB) error {
+	kv.AddInDB(db, "vpc/"+c.Name+"/state", "creating")
+	return vpc.CreateVPC(db, c.Name)
+}
+
+type DeleteVPCCommand struct {
+	Name string
+}
+
+func (c DeleteVPCCommand) Execute(db *badger.DB) error {
+	kv.AddInDB(db, "vpc/"+c.Name+"/state", "deleting")
+	if err := vpc.DeleteVPC(db, c.Name); err != nil {
+		return err
+	}
+	state, err := kv.GetFromDB(db, "vpc/"+c.Name+"/state")
+	if err != nil {
+		return err
+	}
+	if state == "deleted" {
+		kv.DeleteInDB(db, "vpc/"+c.Name)
+	}
+	return nil
+}