Notification System

PROJECT CONTEXT:
I am adding in-app notifications so users learn about relevant events (mentions, orders, system messages).

GOAL:
Implement notification records created by real events, an unread badge, and a notification center with read state.

REQUIREMENTS:
- Notification model linked to a recipient user
- At least two real event triggers that create notifications
- Bell icon with accurate unread count
- Notification center listing with read/unread state
- Mark-as-read (single and all) that persists

CONSTRAINTS:
- Notifications must be created by real events, not seeded fakes
- Unread count must match the database truth
- Clicking a notification should lead somewhere relevant

DEFINITION OF DONE:
- Triggering the real event creates a notification for the right user
- The unread badge increments and is accurate
- Opening/reading persists and decrements the badge
- Notifications survive refresh and are user-scoped

COMMON FAILURES TO AVOID:
- A bell with a hardcoded red dot
- Notifications array in local state, lost on refresh
- Everyone receiving everyone's notifications
- Mark-as-read resetting after reload