Set tabs margin-bottom to 20px ...

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Add export modal with filename prompt, fix spacing ...

- Export now opens a modal asking for filename before saving
- Added live preview of the final filename in the modal
- Added margin-top to tabs and mode-selector for better spacing
- Added CSS utility classes for spacing

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Add explicit mode switcher: Sum vs Payouts ...

- Added chip-group toggle between 'Сумма' and 'Выплаты' modes
- In Sum mode: S is readonly/computed, Z is manual input
- In Payout mode: Z is readonly/computed, S is manual input
- Removed confusing auto-calculation logic for single missing field
- Mode persists in localStorage and export/import
- Updated docs with clear explanation of both modes
- Added input-readonly styling for disabled fields

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Redesign with tabs, fix icons, update artist list ...

- Replaced card-based input sections with tabs (Parameters / Royalties / Artists)
- Removed ph-currency-rub and ph-hand-coins (missing icons)
- Added ph-currency-circle-dollar and ph-coins instead
- Updated artist list to real names
- Added tab switching logic inline in index.html
- Cleaned up CSS styles for new layout

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Add calculation docs and redesign UI with better components ...

- Added docs/calculations.md explaining formula, Base, royalties, auto-calc
- Redesigned UI using Cards, Metric Cards, Alerts, Badges, Page Header
- Fixed icon buttons using `with-icon` class
- Replaced description-list summary with metric cards grid
- Added accent styling for total S metric card
- Updated message display to use alert components
- Fixed duplicate export button IDs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Initial implementation of fire show calculator ...

- Added gnexus-ui-kit as git submodule
- Created index.html with calculator UI
- Implemented formula solver for one unknown variable
- Added artist roster with role assignment
- Calculated royalties based on net amount after material costs
- Added localStorage persistence and JSON export/import
- Created docs/plan.md with project documentation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>