chore: add migrations to git

migrations/20260331000002_create_rooms.exs

@@ -0,0 +1,18 @@
+defmodule Localiser.Repo.Migrations.CreateRooms do
+  use Ecto.Migration
+
+  def change do
+    create table(:rooms) do
+      add :name, :string, null: false
+      add :floor_id, references(:floors, on_delete: :delete_all), null: false
+      add :width, :float
+      add :height, :float
+      add :offset_x, :float
+      add :offset_y, :float
+
+      timestamps(type: :utc_datetime)
+    end
+
+    create index(:rooms, [:floor_id])
+  end
+end