Improve member view table behavior+style, fix config settings (#493)

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

This PR standardizes interactive table behavior and improves settings robustness.
It makes the new hover/focus-visible row highlight the default for clickable tables, keeps sticky first-column behavior configurable (and optimized for member selection UX), and tightens SMTP source-of-truth handling so ENV-based and UI-based configuration do not conflict.

## What has been changed?
- Refactored `CoreComponents.table` to expose interaction state via `data-row-interactive` and moved default row hover/focus styling to CSS.
- Made the new row highlight behavior (`hover` + `:has(:focus-visible)`) the default for clickable zebra tables.
- Kept sticky-first-column as an explicit table option and preserved sticky-specific selection accent behavior.
- Updated member overview table usage to the sticky-first-column mode and refined scrolling behavior (table scrollbar within container, not page-coupled).
- Adjusted table-related tests to validate the new interaction contract (attribute/CSS-driven behavior instead of legacy ring classes).
- Improved SMTP config handling:
  - clearer ENV-vs-Settings behavior (ENV-only mode when host env is set),
  - read-only and warning behavior in global settings UI when required env keys are missing,
  - updated related config/tests/docs.
- Updated docs and changelog (`CHANGELOG.md`, `DESIGN_GUIDELINES.md`, `CODE_GUIDELINES.md`, SMTP concept docs).
- Updated gettext catalogs (`default.pot`, `en`, `de`) for new/changed UI strings.

## 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
- [x] All tests pass
- [ ] axe-core dev tools show no critical or major issues

## Additional Notes
- Branch includes 4 commits:
  - `fix: make sure smtp can be set either via env or ui`
  - `fix: make horizontal scrollbars sticky to bottom`
  - `docs: update changelog`
  - `feat: make checkbox column in member view sticky`
- Full fast suite passed (`mix test --exclude slow --exclude ui`): 2017 tests, 0 failures (plus expected non-failing warning logs in test output).
- Reviewer focus areas:
  1. **Cross-table UX consistency** after moving row interaction styling to component/CSS contract.
  2. **Sticky table behavior** (selection accent stripe, zebra background, keyboard focus visibility).
  3. **SMTP precedence and UI constraints** in global settings when ENV mode is active.
  4. **Regression risk in tests** that previously asserted ring-based row classes.
- No breaking API changes expected; behavior change is primarily visual/interaction-level and intentional.

Reviewed-on: #493
Co-authored-by: Simon <s.thiessen@local-it.org>
Co-committed-by: Simon <s.thiessen@local-it.org>

lib/mv/config.ex

@@ -470,56 +470,77 @@ defmodule Mv.Config do
   # ---------------------------------------------------------------------------
 
   @doc """
-  Returns SMTP host. ENV `SMTP_HOST` overrides Settings.
+  Returns SMTP host.
+
+  Policy:
+  - ENV-only mode (`SMTP_HOST` set): read from ENV `SMTP_HOST`
+  - Settings mode: read from Settings only
   """
   @spec smtp_host() :: String.t() | nil
   def smtp_host do
-    smtp_env_or_setting("SMTP_HOST", :smtp_host)
-  end
-
-  @doc """
-  Returns SMTP port as integer. ENV `SMTP_PORT` (parsed) overrides Settings.
-  Returns nil when neither ENV nor Settings provide a valid port.
-  """
-  @spec smtp_port() :: non_neg_integer() | nil
-  def smtp_port do
-    case System.get_env("SMTP_PORT") do
-      nil ->
-        get_from_settings_integer(:smtp_port)
-
-      value when is_binary(value) ->
-        case Integer.parse(String.trim(value)) do
-          {port, _} when port > 0 -> port
-          _ -> nil
-        end
+    if smtp_env_mode?() do
+      System.get_env("SMTP_HOST") |> trim_nil()
+    else
+      get_from_settings(:smtp_host)
     end
   end
 
   @doc """
-  Returns SMTP username. ENV `SMTP_USERNAME` overrides Settings.
+  Returns SMTP port as integer.
+
+  Policy:
+  - ENV-only mode (`SMTP_HOST` set): read from ENV `SMTP_PORT`
+  - Settings mode: read from Settings only
+  """
+  @spec smtp_port() :: non_neg_integer() | nil
+  def smtp_port do
+    if smtp_env_mode?() do
+      parse_smtp_port_env(System.get_env("SMTP_PORT"))
+    else
+      get_from_settings_integer(:smtp_port)
+    end
+  end
+
+  @doc """
+  Returns SMTP username.
+
+  Policy:
+  - ENV-only mode (`SMTP_HOST` set): read from ENV `SMTP_USERNAME`
+  - Settings mode: read from Settings only
   """
   @spec smtp_username() :: String.t() | nil
   def smtp_username do
-    smtp_env_or_setting("SMTP_USERNAME", :smtp_username)
+    if smtp_env_mode?() do
+      System.get_env("SMTP_USERNAME") |> trim_nil()
+    else
+      get_from_settings(:smtp_username)
+    end
   end
 
   @doc """
   Returns SMTP password.
 
-  Priority: `SMTP_PASSWORD` ENV > `SMTP_PASSWORD_FILE` (file contents) > Settings.
+  Policy:
+  - ENV-only mode (`SMTP_HOST` set): `SMTP_PASSWORD` > `SMTP_PASSWORD_FILE`
+  - Settings mode: read from Settings only
+
   Strips trailing whitespace/newlines from file contents.
   """
   @spec smtp_password() :: String.t() | nil
   def smtp_password do
-    case System.get_env("SMTP_PASSWORD") do
-      nil -> smtp_password_from_file_or_settings()
-      value -> trim_nil(value)
+    if smtp_env_mode?() do
+      case System.get_env("SMTP_PASSWORD") do
+        nil -> smtp_password_from_file()
+        value -> trim_nil(value)
+      end
+    else
+      get_smtp_password_from_settings()
     end
   end
 
-  defp smtp_password_from_file_or_settings do
+  defp smtp_password_from_file do
     case System.get_env("SMTP_PASSWORD_FILE") do
-      nil -> get_smtp_password_from_settings()
+      nil -> nil
       path -> read_smtp_password_file(path)
     end
   end
@@ -533,11 +554,18 @@ defmodule Mv.Config do
 
   @doc """
   Returns SMTP TLS/SSL mode string (e.g. 'tls', 'ssl', 'none').
-  ENV `SMTP_SSL` overrides Settings.
+
+  Policy:
+  - ENV-only mode (`SMTP_HOST` set): read from ENV `SMTP_SSL`
+  - Settings mode: read from Settings only
   """
   @spec smtp_ssl() :: String.t() | nil
   def smtp_ssl do
-    smtp_env_or_setting("SMTP_SSL", :smtp_ssl)
+    if smtp_env_mode?() do
+      System.get_env("SMTP_SSL") |> trim_nil()
+    else
+      get_from_settings(:smtp_ssl)
+    end
   end
 
   @doc """
@@ -549,12 +577,32 @@ defmodule Mv.Config do
   end
 
   @doc """
-  Returns true when any SMTP ENV variable is set (used in Settings UI for hints).
+  Returns true when SMTP is managed by environment variables.
+
+  Policy: if `SMTP_HOST` is set, SMTP is treated as ENV-only.
   """
-  @spec smtp_env_configured?() :: boolean()
-  def smtp_env_configured? do
-    smtp_host_env_set?() or smtp_port_env_set?() or smtp_username_env_set?() or
-      smtp_password_env_set?() or smtp_ssl_env_set?()
+  @spec smtp_env_mode?() :: boolean()
+  def smtp_env_mode? do
+    smtp_host_env_set?()
+  end
+
+  @doc """
+  Returns missing required SMTP ENV keys for ENV-only mode warnings.
+
+  Required in ENV-only mode:
+  - `SMTP_USERNAME`
+  - one of `SMTP_PASSWORD` or `SMTP_PASSWORD_FILE`
+  """
+  @spec smtp_missing_required_env_keys() :: [String.t()]
+  def smtp_missing_required_env_keys do
+    if smtp_env_mode?() do
+      []
+      |> maybe_add_missing("SMTP_USERNAME", smtp_username_env_set?())
+      |> maybe_add_missing("SMTP_PASSWORD/SMTP_PASSWORD_FILE", smtp_password_env_set?())
+      |> Enum.reverse()
+    else
+      []
+    end
   end
 
   @doc "Returns true if SMTP_HOST ENV is set."
@@ -618,14 +666,18 @@ defmodule Mv.Config do
   @spec mail_from_email_env_set?() :: boolean()
   def mail_from_email_env_set?, do: env_set?("MAIL_FROM_EMAIL")
 
-  # Reads a plain string SMTP setting: ENV first, then Settings.
-  defp smtp_env_or_setting(env_key, setting_key) do
-    case System.get_env(env_key) do
-      nil -> get_from_settings(setting_key)
-      value -> trim_nil(value)
+  defp parse_smtp_port_env(value) when is_binary(value) do
+    case Integer.parse(String.trim(value)) do
+      {port, _} when port > 0 -> port
+      _ -> nil
     end
   end
 
+  defp parse_smtp_port_env(_), do: nil
+
+  defp maybe_add_missing(acc, _label, true), do: acc
+  defp maybe_add_missing(acc, label, false), do: [label | acc]
+
   # Reads an integer setting attribute from Settings.
   defp get_from_settings_integer(key) do
     case Mv.Membership.get_settings() do