chore: add migrations to git

migrations/20260331000001_create_floors.exs

@@ -0,0 +1,11 @@
+defmodule Localiser.Repo.Migrations.CreateFloors do
+  use Ecto.Migration
+
+  def change do
+    create table(:floors) do
+      add :name, :string, null: false
+
+      timestamps(type: :utc_datetime)
+    end
+  end
+end