[Feature]: Enable search multiple categories/tags

[ZL-Asica]

💡 Feature Description

The categories and tags filtering do not support multiple selections at once.

📌 Use Case

As a user, I want to search posts based on different categories/tags (multiple) at once.

🚀 Priority Level

Medium - Crucial but not urgent.

🔄 Alternatives Considered

No response

✔ Checklist

• I have checked that this feature does not already exist.