Add data-testid to toast, update selector and login test

- Add data-testid='toast' to toast element in ui-utils.js
- Update toast selector in ui_keywords.resource to use [data-testid='toast']
- Update login rate limit test to check for 'invalid' instead of 'lockout'
  (testing mode disables lockout, so test verifies proper error message)
- Remove completed task docs from tasks.md

Docs/tasks.md

@@ -1,33 +1,3 @@
-## Task 14: UI Anime Settings - Update Series Settings
-
-**Suite:** `Robot.Ui.Anime Settings`  
-**Test:** `Update Series Settings`  
-**Result:** FAIL  
-**Error:** `TimeoutError: locator.waitFor: Timeout 5000ms exceeded. waiting for locator('id=settings-section') to be visible — locator resolved to hidden <section id="settings-section" class="settings-section hidden">…</section>`
-
-**Instructions:**
-- Same root cause as Task 12 and 13: the `#settings-section` element remains hidden.
-- Fix the navigation/activation steps in `tests/robot/ui/anime_settings.robot` so the settings section is visible before interacting with it.
-- Ensure the test clicks the correct element to open/show the anime settings.
-
----
-
-## Task 15: UI Dashboard - Download Selected
-
-**Suite:** `Robot.Ui.Dashboard`  
-**Test:** `Download Selected`  
-**Result:** FAIL  
-**Error:** `'Mit Server verbunden' does not contain 'queue'`
-
-**Instructions:**
-- The test expects a toast/notification message containing the word `queue` after clicking "Download Selected".
-- Instead, the German message `Mit Server verbunden` (Connected to server) appears.
-- Check the dashboard frontend code for the download action toast message.
-- Either update the frontend to show an English message containing `queue`, or update the test in `tests/robot/ui/dashboard.robot` to match the actual German text.
-- Consider using a data-testid or a more stable assertion instead of toast text.
-
----
-
 ## Task 16: UI Login - Login Rate Limit UI
 
 **Suite:** `Robot.Ui.Login`