feat(desktop): Show project indexing progress in notification bell

[haiphucnguyen]

Problem

When a user opens a project in ProjectView, indexing starts automatically. The
indexing progress is only visible while the user stays on ProjectView - it
renders the progress inline in that screen.

If the user navigates away (e.g. starts a chat, switches to another view), they have
no indication that:

• Indexing is still running in the background
• Indexing has completed successfully
• Indexing has failed

This creates a confusing experience: the user may start chatting expecting RAG to be
available, but the index isn't ready yet - with no feedback.

Root Cause

ProjectIndexer emits IndexingStartedEvent, IndexingQueuedEvent,
IndexingCompletedEvent, and IndexingFailedEvent to EventBus.userEvents, but
NotificationComponents.notificationIcon currently only listens for
UpdateAvailableEvent and ShellErrorEvent. Indexing events are silently dropped.

Proposed Solution

1. Handle indexing events in notificationIcon (NotificationComponents.kt)

The existing LaunchedEffect in notificationIcon already collects from
EventBus.userEvents. Extend notificationEventCard to render cards for:

Event	Icon	Card style
IndexingQueuedEvent	HourglassEmpty	neutral surfaceVariant
IndexingStartedEvent	Sync (animated spin)	neutral surfaceVariant
IndexingCompletedEvent	CheckCircleOutline	tertiaryContainer (green-ish)
IndexingFailedEvent	ErrorOutline	error-tinted surfaceVariant

The card should show:

• Project name (event.projectName)
• Status label (e.g. "Indexing…", "Index ready", "Indexing failed")
• Timestamp
• For IndexingCompletedEvent: files indexed count (event.filesIndexed)
• For IndexingFailedEvent: error message + selectable stack trace (same pattern as
  ShellErrorEvent cause expansion)
• For IndexingStartedEvent / IndexingQueuedEvent: auto-dismiss the card once
  IndexingCompletedEvent or IndexingFailedEvent arrives for the same project
  (replace in the events list by projectId)

2. Auto-open bell for terminal states

Mirror the existing behaviour for UpdateAvailableEvent and ShellErrorEvent:

• IndexingFailedEvent → auto-open the notification popup (user must know)
• IndexingCompletedEvent → increment unread badge only (don't force-open)

3. Deduplicate in-progress cards

If IndexingStartedEvent arrives for a project that already has a
IndexingQueuedEvent card, replace the queued card in-place rather than appending.
Use projectId as the deduplication key.

Files Affected

File	Change
NotificationComponents.kt	Handle IndexingStartedEvent, IndexingQueuedEvent, IndexingCompletedEvent, IndexingFailedEvent in notificationEventCard and notificationIcon
i18n resource files	Add keys: event.indexing.started, event.indexing.queued, event.indexing.completed, event.indexing.failed, event.indexing.files_indexed