Integrate CRUD APIs for food items

[gTanusri]

Summary

• Integrated the admin Food Items UI with the existing FoodController backend APIs.
• Added backend-backed food item listing, category filtering, search, pagination, add/edit, delete, and availability toggle flows.
• Added frontend validation for required fields, price values, category selection, and image file/URL inputs.
• Added loading, empty, error, and toast feedback states for food item CRUD actions.
• Updated food endpoint authorization so secure update, delete, and PATCH availability requests work with the app's existing authorities.

Issue

Closes #229