feat: simplify App component and enhance Canvas collaboration features

[Shreyanshi210205]

Description

Currently, when users visit the homepage, they are immediately prompted to join a collaboration room before they can start drawing.
This creates a poor user experience. This PR implements a local-first drawing mode where users can begin sketching right away, and choose to collaborate only when they explicitly opt in.

1.Local-First Experience
-Removed the “Join Room” modal from automatically appearing on page load.
-The app now opens directly to a blank canvas ready for drawing.
-No socket connections or events are triggered until collaboration is enabled.
2.Collaborate Button
-Added a new “Collaborate” / “Join Room” button in the toolbar.
-When clicked, this opens the room-joining modal where the user can enter a room ID to start collaborating.
3.Dynamic Collaboration Toggle
-Once a user joins or creates a room:
-WebSocket communication is activated.
-All drawing actions are synchronized in real time across connected clients.
-If not joined, drawing actions stay completely local and are not emitted.
4. Disabled Sockets in Local Mode
-In the default local mode, socket.emit() calls are conditionally blocked (if (joined && socket) checks added).

Semver Changes

• Patch (bug fix, no new features)
• Minor (new features, no breaking changes)
• Major (breaking changes)

Issues

#26

Checklist

• I have read the Contributing Guidelines.