- Add SyncProgress.kt: Data class for entire sync lifecycle UI state
- Add SyncPhase enum: IDLE, PREPARING, UPLOADING, DOWNLOADING, IMPORTING_MARKDOWN, COMPLETED, ERROR
- Rewrite SyncStateManager.kt: SyncProgress (StateFlow) is single source of truth
- Remove pre-set phases: CHECKING_SERVER and SAVING cause flickering
- UPLOADING phase only set when actual uploads happen
- DOWNLOADING phase only set when actual downloads happen
- IMPORTING_MARKDOWN phase only set when feature enabled
- Add onProgress callback to uploadLocalNotes() with uploadedCount/totalToUpload
- Add onProgress callback to downloadRemoteNotes() for actual downloads only
- Progress display: x/y for uploads (known total), count for downloads (unknown)
- Add SyncProgressBanner.kt: Unified banner (replaces dual system)
- Update SyncStatusBanner.kt: Kept for legacy compatibility, only COMPLETED/ERROR
- Update MainViewModel.kt: Remove _syncMessage, add syncProgress StateFlow
- Update MainScreen.kt: Use only SyncProgressBanner (unified)
- Update ComposeMainActivity.kt: Auto-hide COMPLETED (2s), ERROR (4s) via lifecycle
- Add strings.xml (DE+EN): sync_phase_* and sync_wifi_only_error
- Banner appears instantly on sync button click (PREPARING phase)
- Silent auto-sync (onResume) completely silent, errors always shown
- No misleading counters when nothing to sync
Closes #IMPL_006
df37d2a47c