fix(tasks): use correct label when re-opening a completed task (#7792)

The context menu's toggle-done button always showed "Mark as completed"
regardless of the task's done state, because both branches of the ternary
on line 151 of task-context-menu-inner.component.html referenced MARK_DONE.
The matching icon already conditionally rendered undo vs check based on
isDone, so only the label was misleading.

Add a MARK_UNDONE i18n key ("Mark as not completed") and use it on the
isDone branch, mirroring the existing icon switch.

Closes #7785

src/app/features/tasks/task-context-menu/task-context-menu-inner/task-context-menu-inner.component.html

@@ -148,7 +148,9 @@
         } @else {
           <mat-icon>check</mat-icon>
         }
-        {{ (task.isDone ? T.F.TASK.CMP.MARK_DONE : T.F.TASK.CMP.MARK_DONE) | translate }}
+        {{
+          (task.isDone ? T.F.TASK.CMP.MARK_UNDONE : T.F.TASK.CMP.MARK_DONE) | translate
+        }}
       </span>
       <span class="key-i">{{ kb.taskToggleDone }}</span>
     </button>

src/app/t.const.ts

@@ -1680,6 +1680,7 @@ const T = {
         ESTIMATE: 'F.TASK.CMP.ESTIMATE',
         FOCUS_SESSION: 'F.TASK.CMP.FOCUS_SESSION',
         MARK_DONE: 'F.TASK.CMP.MARK_DONE',
+        MARK_UNDONE: 'F.TASK.CMP.MARK_UNDONE',
         MOVE_TO_BACKLOG: 'F.TASK.CMP.MOVE_TO_BACKLOG',
         MOVE_TO_OTHER_PROJECT: 'F.TASK.CMP.MOVE_TO_OTHER_PROJECT',
         MOVE_TO_REGULAR: 'F.TASK.CMP.MOVE_TO_REGULAR',

src/assets/i18n/en.json

@@ -1642,6 +1642,7 @@
         "ESTIMATE": "Estimate",
         "FOCUS_SESSION": "Start focus session",
         "MARK_DONE": "Mark as completed",
+        "MARK_UNDONE": "Mark as not completed",
         "MOVE_TO_BACKLOG": "Move to backlog",
         "MOVE_TO_OTHER_PROJECT": "Move to project",
         "MOVE_TO_REGULAR": "Move to regular list",