feat: full-screen glass editor, user migration, and UI improvements

[BandiAkarsh]

Editor Improvements:

• Add full-screen glass background with gradient orbs and grid
• Apply glass effect to editor content area with blur and transparency
• Make editor text area larger and fill available space
• Add glass styling to Share/Export buttons
• Increase spacing between Share/Export buttons (12px gap)
• Add separator line between toolbar groups

User Migration System:

• Add migration check for existing users from old version
• Show migration modal for users without passwords
• Allow existing users to set password without losing data
• Auto-login after successful migration

Auth Store Updates:

• Add checkMigration() function to detect users needing password setup
• Add migrateUser() function to upgrade existing accounts
• Export MigrationStatus interface

UI Polish:

• Add smooth transitions and hover effects to glass buttons
• Improve dark mode support for glass elements
• Add responsive styles for migration modal

Fixes issues:

• Small text editor box (now fills screen with glass bg)
• Share/Export buttons too close (now properly spaced)
• Existing users losing access (now prompted to set password)