Window Management Improvements

This update focused on making the JishOS desktop feel much closer to a real operating system.

What’s new:

• 🖱️ Added window resizing from all four edges with minimum size limits.
• 📏 Fixed windows resizing beyond the desktop boundaries.
• 🪟 Fixed newly opened windows occasionally appearing partially off-screen due to CSS positioning issues.
• 📐 Implemented cascading window offsets so each new window opens slightly offset from the previous one.
• 🎯 Added window focus, allowing a clicked window to move to the front of the stack.

This update significantly improves the overall desktop experience and lays the groundwork for future features like minimizing, maximizing, and window snapping.