🖍️ Color n' Constant Changes (#739)

[EightBitByte]

Summary

This PR completes the systematic elimination of all remaining hardcoded hex color values ("magic constants") across the Next.js frontend, centralizing them as semantically named CSS variables in globals.css for robust dark/light mode consistency. It also integrates key UI state refactors, optimization/performance fixes for dishes rendering, and addresses merge conflict cleanups.

Changes

🎨 Color & Theme Centralization (Magic Constants Clean-up)

• CSS Variables Definition (globals.css): Expanded variables for surfaces (--surface-modal, --surface-dialog, --surface-tinted, --surface-scroll, --surface-elevated), borders (--border-input, --accent-border), text colors, calendars, and tabs.
• Component Styling Migrations:
  • Converted custom/arbitrary hex codes to var(...) references inside:
    • Modals/Drawers: food-dialog-content.tsx, food-drawer-content.tsx, event-dialog-content.tsx, event-drawer-content.tsx, ingredients-dialog.tsx.
    • Views/Pages: calendar-view.tsx, my-foods/page.tsx, events/page.tsx, edit-preferences-content.tsx.
    • Header/Controls: restaurant-filters.tsx, mobile-actions.tsx, desktop-tabs.tsx.
  • Aligned custom opacity variations for accents to use #8EC5FF33 consistently across nutrition-goals.tsx, nutrition-breakdown.tsx, mobile-nutrition-bars.tsx, meal-search.tsx, and mobile-calorie-card.tsx.

⚡ Performance & State Management Refactoring (Restaurant UI)

• Memoized Dishes Filtering: Pre-computed filtered dishes map per station via useMemo in dishes-view.tsx. This avoids redundant getDietaryConflicts computations on every render when switching views (e.g. toggling isCompactView or stations).
• Zustand UI State Integration: Migrated local restaurant view states (such as isCompactView, showPreferencesOnly, selectedStation) to useRestaurantUIStore or resolved them in a central useRestaurantPage custom hook.
• Clean Interface Controls: Streamlined restaurant-controls.tsx and restaurant-page.tsx by reducing drilldown props and offloading lifecycle operations to hooks/stores.

Closes #739, #727, #734, #728