Android: eliminate task list flicker on cold start

[dkhalife]

Problem

When opening the Android app, the cached task list flashes multiple times before stabilizing: labels disappear and reappear, and the whole cycle repeats two or three times.

Root causes

1. Intra-refresh flicker — SyncCoordinator.refreshAll() upserts tasks and replaces their label cross-refs one row at a time. TaskDao.replaceLabels does DELETE FROM task_labels then re-inserts; each write invalidates the @Transaction @Query backing observeTasks(), so the Flow emits intermediate states where tasks temporarily have no labels.

2. Three refresh cycles per cold open — all of these triggered a full refreshAll():

   • TaskWizardApplication.onCreate → syncCoordinator.syncOnce()
   • TaskListViewModel.init → refreshTasks()
   • TaskListViewModel.init → labelRepository.refreshLabels() (which also just delegates to syncOnceBlocking)

   They serialize behind the coordinator mutex and each one produces its own flicker cycle.

Fix

• Wrap SyncCoordinator.refreshAll() in db.withTransaction { ... } so Room batches table invalidations and emits a single Flow update per sync.
• Drop the redundant labelRepository.refreshLabels() call from TaskListViewModel.init — refreshTasks() already refreshes labels via the coordinator.
• Drop the eager syncCoordinator.syncOnce() from TaskWizardApplication.onCreate; the first screen's ViewModel triggers a refresh, and the NetworkMonitor availability listener still kicks one when connectivity flips on.

Net result on cold open: a single refresh cycle with a single UI update — no flash.

[Copilot]

Pull request overview

This PR targets Android cold-start task list flicker by reducing redundant sync triggers and attempting to batch Room invalidations so task/label observers emit fewer intermediate states during refresh.

Changes:

• Removed an extra label refresh trigger from TaskListViewModel initialization to avoid redundant full refresh cycles.
• Removed the eager syncCoordinator.syncOnce() call from TaskWizardApplication.onCreate, relying on other refresh triggers instead.
• Wrapped SyncCoordinator.refreshAll() in a Room transaction via db.withTransaction { ... }.

Show a summary per file

File	Description
android/app/src/main/java/com/dkhalife/tasks/viewmodel/TaskListViewModel.kt	Removes redundant label refresh during VM init to reduce repeated refresh/flicker cycles.
android/app/src/main/java/com/dkhalife/tasks/TaskWizardApplication.kt	Removes eager startup sync; keeps sync-on-connectivity callback; minor MSAL type import cleanup.
android/app/src/main/java/com/dkhalife/tasks/data/sync/SyncCoordinator.kt	Adds DB-level transaction wrapper around refresh to reduce intermediate Room observer emissions.

Copilot's findings

• Files reviewed: 3/3 changed files
• Comments generated: 2