feat(ui): standardize design system, modals, sidebar, and form inputs
- Implement unified design system tokens, 10px radius, and IRANSans typography
- Modernize sidebar with Gemini-style collapsed expander, square 1:1 items, and elevated profile flyout
- Standardize all modal dialogs with 16px padding, fixed header/footer, 16px medium title, and sticky bottom actions
- Refactor DealFormView and CustomFieldsSection with standard UiField, UiInput, and UiSelect components
- Add draggable bottom-left QuickCreate floating action button