Improve UX of join requests and fix minor bugs (#492)

## Description of the implemented changes
The changes were:
- [x] Bugfixing
- [x] New Feature
- [ ] Breaking Change
- [ ] Refactoring

This PR improves the join-request flow and presentation quality, fixes several data-display issues in join/join-request screens, and adds a usability improvement in global settings (directly opening the join link). It also includes dependency updates and changelog maintenance.

## What has been changed?
- Join form (`JoinLive`) now renders inputs based on actual field types (including checkbox/date/number/email behavior instead of generic text-only handling).
- Join form custom-field labels are resolved from configured custom fields (fallback remains safe if lookup fails).
- Join-request details page (`JoinRequestLive.Show`) now:
  - resolves and shows custom field names instead of raw IDs,
  - formats boolean-like values (`on/true/1`, `off/false/0`) as localized `Yes/No`,
  - formats ISO date strings for better readability,
  - keeps legacy field handling while improving output consistency.
- Join-request detail layout was improved semantically and visually (`dl/dt/dd` structure for label/value rows).
- Global settings page now includes an **Open** button for the join URL (`target="_blank"`, `rel="noopener noreferrer"`, ARIA label).
- Added/updated tests around:
  - join field type rendering,
  - custom field labels in join-request views,
  - related auth/global-settings behavior.
- Updated translations (`default.pot`, `en`, `de`) for new UI strings.
- Updated dependencies/tooling (`mix.lock`, `mix.exs`, CI/renovate-related updates).
- Updated `CHANGELOG.md` entries for unreleased changes.

## Definition of Done
### Code Quality
- [x] No new technical depths
- [x] Linting passed
- [x] Documentation is added were needed

### Accessibility
- [x] New elements are properly defined with html-tags
- [x] Colour contrast follows WCAG criteria
- [x] Aria labels are added when needed
- [x] Everything is accessible by keyboard
- [x] Tab-Order is comprehensible
- [x] All interactive elements have a visible focus

### Testing
- [x] Tests for new code are written
- [ ] All tests pass
- [ ] axe-core dev tools show no critical or major issues

## Additional Notes
- Reviewer focus areas:
  - `lib/mv_web/live/join_live.ex`: input type derivation and custom field lookup strategy (`authorize?: false` read path used intentionally for field metadata).
  - `lib/mv_web/live/join_request_live/show.ex`: value-formatting logic (especially backward compatibility for legacy `form_data` payloads).
  - `lib/mv_web/live/global_settings_live.ex`: external-link behavior and accessibility attributes.
- The branch also contains dependency update commits; please review lockfile and CI-related changes separately from functional join/join-request changes.

Reviewed-on: #492
Co-authored-by: Simon <s.thiessen@local-it.org>
Co-committed-by: Simon <s.thiessen@local-it.org>

test/mv_web/live/join_request_live/show_test.exs

@@ -0,0 +1,124 @@
+defmodule MvWeb.JoinRequestLive.ShowTest do
+  @moduledoc """
+  Tests for join request detail view label rendering.
+
+  Focus: applicant data labels for custom fields should use custom field names,
+  not raw UUIDs.
+  """
+  use MvWeb.ConnCase, async: false
+
+  import Phoenix.LiveViewTest
+
+  alias Mv.Fixtures
+  alias Mv.Membership
+  alias MvWeb.Helpers.DateFormatter
+
+  setup do
+    {:ok, settings} = Membership.get_settings()
+
+    saved = %{
+      join_form_enabled: settings.join_form_enabled,
+      join_form_field_ids: settings.join_form_field_ids,
+      join_form_field_required: settings.join_form_field_required
+    }
+
+    on_exit(fn ->
+      {:ok, current_settings} = Membership.get_settings()
+
+      Membership.update_settings(current_settings, %{
+        join_form_enabled: saved.join_form_enabled,
+        join_form_field_ids: saved.join_form_field_ids || [],
+        join_form_field_required: saved.join_form_field_required || %{}
+      })
+    end)
+
+    :ok
+  end
+
+  describe "custom field labels in applicant data" do
+    @tag role: :normal_user
+    test "renders custom field name instead of custom field UUID", %{conn: conn} do
+      system_actor = Mv.Helpers.SystemActor.get_system_actor()
+      {:ok, settings} = Membership.get_settings()
+
+      {:ok, custom_field} =
+        Membership.create_custom_field(
+          %{
+            name: "Emergency contact",
+            value_type: :string
+          },
+          actor: system_actor
+        )
+
+      {:ok, _} =
+        Membership.update_settings(settings, %{
+          join_form_enabled: true,
+          join_form_field_ids: ["email", custom_field.id],
+          join_form_field_required: %{"email" => true, custom_field.id => false}
+        })
+
+      join_request =
+        Fixtures.submitted_join_request_fixture(%{
+          form_data: %{custom_field.id => "Alice Example"}
+        })
+
+      {:ok, view, _html} = live(conn, "/join_requests/#{join_request.id}")
+
+      assert has_element?(view, "dt", "#{custom_field.name}:")
+      assert has_element?(view, "dd", "Alice Example")
+      refute has_element?(view, "dt", "#{custom_field.id}:")
+    end
+
+    @tag role: :normal_user
+    test "formats boolean/date values and renders status in aligned row", %{conn: conn} do
+      system_actor = Mv.Helpers.SystemActor.get_system_actor()
+      {:ok, settings} = Membership.get_settings()
+
+      {:ok, boolean_field} =
+        Membership.create_custom_field(
+          %{
+            name: "Privacy accepted",
+            value_type: :boolean
+          },
+          actor: system_actor
+        )
+
+      {:ok, date_field} =
+        Membership.create_custom_field(
+          %{
+            name: "Birth date",
+            value_type: :date
+          },
+          actor: system_actor
+        )
+
+      {:ok, _} =
+        Membership.update_settings(settings, %{
+          join_form_enabled: true,
+          join_form_field_ids: ["email", boolean_field.id, date_field.id],
+          join_form_field_required: %{
+            "email" => true,
+            boolean_field.id => false,
+            date_field.id => false
+          }
+        })
+
+      join_request =
+        Fixtures.submitted_join_request_fixture(%{
+          form_data: %{
+            boolean_field.id => "on",
+            date_field.id => "2000-01-12"
+          }
+        })
+
+      {:ok, view, _html} = live(conn, "/join_requests/#{join_request.id}")
+
+      assert has_element?(view, "dt", "Privacy accepted:")
+      assert has_element?(view, "dd", "Yes")
+      assert has_element?(view, "dt", "Birth date:")
+      assert has_element?(view, "dd", DateFormatter.format_date(~D[2000-01-12]))
+      assert has_element?(view, "dt", "Status:")
+      assert has_element?(view, "dd", "Submitted")
+    end
+  end
+end