Calendar polish, Todo UX, and mobile stability
- Added a 3-day calendar detail carousel with full-height adjacent day previews and cross-day task dragging.
- Improved calendar interactions with task selection, double-click edit, click-away deselect, and keyboard delete behavior.
- Updated calendar styling and behavior: light-mode detail views, red highlight for today, and removed per-day “X tasks” count labels.
- Kept the Spaces rail toggle in the top navbar with dynamic Show/Hide labeling and removed the old right-rail hide button.
- Improved Todo creation flow with Enter-to-add and replaced the “Also share with” mini-scroll picker with a standard dropdown.
- Made Escape behavior safer by preventing unexpected mode switches while working in the Todo page.
- Fixed legal pages (/privacy and /terms) to follow the active light/dark theme.
- Hardened mobile behavior by disabling unstable fullscreen fallback controls on touch devices.