feat(ui): introduce core Querya UI Kit standard widgets in lib/shared/widgets (#1038)

[ZhuchkaTriplesix]

Closes #1038

Description

Introduces standard Querya UI Kit components in lib/shared/widgets/ with full runtime theme adaptability (VS Code themes & dark/light palettes) and unified ergonomics across the application.

Components

1. QueryaModalDialog & QueryaConfirmDialog (lib/shared/widgets/querya_modal_dialog.dart):
   • Standard modal shell based on QueryaDialogCard and showAppDialog.
   • Declarative confirmation dialog supporting standard and destructive modes.
2. QueryaIconButton & QueryaToolbarButton (lib/shared/widgets/querya_icon_button.dart):
   • Density presets: dense (28x28px) and standard (32x32px).
   • Built-in material.Tooltip with kQueryaTooltipWait.
   • Themed hover/active/destructive states.
3. QueryaSearchField (lib/shared/widgets/querya_search_field.dart):
   • Filter/search field with built-in debounce, search icon, shortcut hint, and quick clear button (Esc / ✕).
4. QueryaSpinner (lib/shared/widgets/querya_spinner.dart):
   • Size presets: sm (14px), md (20px), lg (32px).
   • Theme-bound accent color and optional trailing label.
5. QueryaBadge (lib/shared/widgets/querya_badge.dart):
   • Semantic typed badges: primaryKey, foreignKey, dataType, status, readOnly based on QueryaSemanticPalette.
6. QueryaEmptyState (lib/shared/widgets/querya_empty_state.dart):
   • Unified placeholder for empty queries, tables, and search results.

Tests

• Added 6 dedicated widget test suites in test/shared/widgets/ covering all components, density presets, and theme bindings.