Remove HA/Python components and add Phoenix LiveView dashboard

- Remove home-assistant-integration/ and dev-config/
- Remove Python/HA dependencies from flake.nix
- Add Phoenix LiveView dashboard with clean Elixir-only stack
- Add Node.js and PostgreSQL for Phoenix development
- Much cleaner monorepo architecture focusing on Elixir ecosystem

Next: Connect dashboard to MQTT for real-time host monitoring

server/dashboard/test/dashboard_web/controllers/error_html_test.exs

@@ -0,0 +1,14 @@
+defmodule DashboardWeb.ErrorHTMLTest do
+  use DashboardWeb.ConnCase, async: true
+
+  # Bring render_to_string/4 for testing custom views
+  import Phoenix.Template
+
+  test "renders 404.html" do
+    assert render_to_string(DashboardWeb.ErrorHTML, "404", "html", []) == "Not Found"
+  end
+
+  test "renders 500.html" do
+    assert render_to_string(DashboardWeb.ErrorHTML, "500", "html", []) == "Internal Server Error"
+  end
+end

server/dashboard/test/dashboard_web/controllers/error_json_test.exs

@@ -0,0 +1,12 @@
+defmodule DashboardWeb.ErrorJSONTest do
+  use DashboardWeb.ConnCase, async: true
+
+  test "renders 404" do
+    assert DashboardWeb.ErrorJSON.render("404.json", %{}) == %{errors: %{detail: "Not Found"}}
+  end
+
+  test "renders 500" do
+    assert DashboardWeb.ErrorJSON.render("500.json", %{}) ==
+             %{errors: %{detail: "Internal Server Error"}}
+  end
+end

server/dashboard/test/dashboard_web/controllers/page_controller_test.exs

@@ -0,0 +1,8 @@
+defmodule DashboardWeb.PageControllerTest do
+  use DashboardWeb.ConnCase
+
+  test "GET /", %{conn: conn} do
+    conn = get(conn, ~p"/")
+    assert html_response(conn, 200) =~ "Peace of mind from prototype to production"
+  end
+end

server/dashboard/test/support/conn_case.ex

@@ -0,0 +1,37 @@
+defmodule DashboardWeb.ConnCase do
+  @moduledoc """
+  This module defines the test case to be used by
+  tests that require setting up a connection.
+
+  Such tests rely on `Phoenix.ConnTest` and also
+  import other functionality to make it easier
+  to build common data structures and query the data layer.
+
+  Finally, if the test case interacts with the database,
+  we enable the SQL sandbox, so changes done to the database
+  are reverted at the end of every test. If you are using
+  PostgreSQL, you can even run database tests asynchronously
+  by setting `use DashboardWeb.ConnCase, async: true`, although
+  this option is not recommended for other databases.
+  """
+
+  use ExUnit.CaseTemplate
+
+  using do
+    quote do
+      # The default endpoint for testing
+      @endpoint DashboardWeb.Endpoint
+
+      use DashboardWeb, :verified_routes
+
+      # Import conveniences for testing with connections
+      import Plug.Conn
+      import Phoenix.ConnTest
+      import DashboardWeb.ConnCase
+    end
+  end
+
+  setup _tags do
+    {:ok, conn: Phoenix.ConnTest.build_conn()}
+  end
+end

server/dashboard/test/test_helper.exs

@@ -0,0 +1 @@
+ExUnit.start()