Fix redundant React effect in the dashboard and standardize auth fetching in the layout to use the shared API client.

[nazarli-shabnam]

1. Duplicate useEffect in DashboardPage

• File: apps/frontend/src/pages/dashboard/DashboardPage.tsx
• Lines: 86–90 and 100–104
• Issue: Both effects set selectedWorkspaceId when workspaces loads; redundant and can cause extra renders.
• Fix: Remove the duplicate effect (lines 100–104).

2. Direct fetch in DashboardLayout

• File: apps/frontend/src/components/layout/DashboardLayout.tsx
• Lines: 43–52
• Issue: Uses raw fetch for /api/auth/me instead of apiFetch; token handling may be inconsistent with the rest of the app.
• Fix: Replace with apiFetch for consistent auth headers and error handling.

3. Redis connection per broadcast (optional / lower priority)

• File: api/app/app/websocket/manager.py
• Issue: broadcast_to_board creates a new Redis client and closes it each time; can be inefficient under load.
• Fix: Consider a shared Redis client or connection pool for publish operations.