Session tabs:
- Add SessionTabs component at the bottom of terminal area
- Preserve session state when switching between tabs
- Status indicator (connected/connecting/error)
- Auto-resize terminal when tab becomes active

Platform-specific updates:
- macOS: Manual download from GitHub (notification with link)
- Windows: Silent auto-update without installer UI
- Linux: Add AppImage and deb builds to release workflow

Organization member management:
- Admin/owner can change member roles
- Admin/owner can remove members from organization
- Role badges with colors (owner=yellow, admin=blue)
- Dropdown menu for member actions