[Feature]: Show workout completion indicator in the daily diary

[G5K-org]

Problem

When browsing the Diary screen after finishing a workout, there is no visual indicator to distinguish completed workout sessions from sessions that were just logged. Users have no way to tell at a glance whether they've already done their workout for the day.

Proposed Solution

Add a small "Done" badge to completed workout session rows in the Diary screen.

Implementation approach (mobile only, no server changes required):

1. src/stores/activeWorkoutStore.ts — Add a completedSessionIds: Record<string, true> field to the persisted state. When clearWorkout() is called and the workout was fully complete (activeSetId === null), record the session ID before resetting all other state. This field survives the clear action and is persisted to AsyncStorage.

2. src/components/SwipeableExerciseRow.tsx — Read completedSessionIds from the store. If the current session's ID is present, render a small green "Done" badge next to the source label. The badge persists across cold starts.

Why this approach:

• No server changes — ExerciseSessionResponse has no completion flag; tracking is client-side only
• Uses the existing activeWorkoutStore AsyncStorage persist layer
• The indicator appears after the user taps the ✓ checkmark to dismiss the finished workout

Affected Files

• SparkyFitnessMobile/src/stores/activeWorkoutStore.ts
• SparkyFitnessMobile/src/components/SwipeableExerciseRow.tsx

Acceptance Criteria

• Complete all sets in a preset workout and tap the finish checkmark
• Navigate to Diary — the finished workout row shows a green "Done" badge
• Background/kill the app and reopen — badge is still visible
• A workout session that was not completed via the active tracker shows no badge

[apedley]

This makes sense in the context of workout plans. We might want this reflected on the web UI so I think adding a db column and tracking it server side is a good idea.