Add Wellby extension and refine game UI

[MichelleVi09]

This PR adds a browser-side Wellby extension and refines the break-mode game UI.

Changes include:

• adding a floating Wellby browser extension with mood/stress check-ins
• syncing extension state with the Wellby app, including task context and theme
• adding extension timer/theme support from settings
• refining the break-mode game UI for Snake, Tic Tac Toe, Chess, and UNO
• improving game layout, readability, and title/header presentation