Show welcome screen when user has zero tasks👋

[anoopcodehack]

Description

New users currently see a completely empty board with no guidance on what to do next. Add a friendly welcome message that shows up when there are zero tasks.

File

client/src/pages/Dashboard.jsx

Tasks

• Check if tasks.length === 0
• If true, render a welcome screen instead of the empty board:
  • 👋 emoji + "Welcome to your board!" heading
  • Short message: "You don't have any tasks yet. Click + Add card to create your first one."
  • A "+ Add your first card" button that triggers the same action as the existing add-card button
• Match existing dark mode styling

Acceptance Criteria

• Empty board shows the welcome message instead of a blank screen
• Clicking the button opens the add-card flow (same as normal + Add card)
• Message disappears once at least one task exists

Suggested code

```jsx
if (tasks.length === 0) {
return (

👋

Welcome to your board!

You don't have any tasks yet. Click + Add card to create your first one.

+ Add your first card

);
}
```

[Himanshu9097]

Hi! I'd like to work on this issue. Could you please assign it to me?

[anoopcodehack]

Thanks for your interest, @Himanshu9097! I've assigned this issue to you. Feel free to open a PR once it's ready. Let me know if you have any questions.

[anoopcodehack]

Hey, your PR has been merged! You're officially a DevBoard contributor now!

If you enjoyed contributing and found the project useful, consider leaving a ⭐ on the repo — it really helps more developers discover the project and keeps the community growing!

Also feel free to pick up another issue anytime — always happy to have you here! 🙌