[US-016] Follow and unfollow stores #6
Description
User Story
As a buyer,
I want to follow my favorite stores,
So that I get notified when they go live and see them first in my feed.
Acceptance Criteria
- Follow button on store profile and store cards
- Followed stores appear in "Following" tab
- Unfollow with confirmation on long-press or profile page
- Follower count updates in real-time
- Following status persists across app sessions