refactor: TUI state extraction, screener table, and multi-view navigation

[HanSoBored]

Summary

• Extracted TUI state into dedicated modules: PopupState, MouseState, ScreenerService for cleaner separation of concerns
• Added modular key handler with NavResult enum for clean event dispatch across navigation, screener, and contract filter handlers
• Added shared table utilities (table_common) and new screener_table widget with sortable columns (Change%, Volume, Symbol)
• Added ContractType model with LP/LF/IP/IF filtering via keyboard shortcuts (1-4, 0)
• Improved multi-view navigation between Symbol List (l), Screener (s), and Stats Dashboard (Tab)
• Refactored runner with generation tracking for stale-result detection and extracted timeout constants
• Updated README with new features, key bindings, and TUI architecture documentation

Commits

1. docs(readme) — Update with multi-view TUI, contract type filtering, and screener table features
2. refactor(models) — Add ContractType enum and integrate into Symbol model
3. refactor(tui) — Extract PopupState, MouseState, and ScreenerService for cleaner state management
4. refactor(tui) — Add modular key handler with NavResult and multi-view navigation
5. refactor(tui) — Add shared table utilities and screener table widget
6. refactor(tui) — Improve runner with generation tracking and timeout constants
7. refactor(tui) — Improve footer with active filter display and header with contract types
8. refactor(screener) — Improve calculator with better sorting and fetcher with error handling
9. refactor(models) — Improve price parsing and statistics with zero-copy iteration
10. refactor(cli) — Improve argument parsing and main with screener integration

Verification

• ✅ cargo build — Clean
• ✅ cargo test — 77 tests pass
• ✅ cargo clippy — No warnings

[HanSoBored]

LGTM