Add notification preferences for students and teachers

[knoxiboy]

Description

Let users control which in-app and email notifications they receive.

Problem

The usersTable already has emailNotificationsEnabled (line 17), notificationPreference (line 18, values: instant/daily/weekly/none), and the Inngest functions respect these preferences. However: there is no UI for users to manage these preferences; in-app notifications have no category-based filtering; /api/user/preferences/route.ts updates preferences but without Zod validation.

Proposed Solution

1. Build a notification preferences UI in the user profile/settings area. 2. Add category-based preferences (replies, mentions, classroom activity, teacher alerts, weekly summaries). 3. Add Zod validation to the preferences route.

Files Affected

• src/app/api/user/preferences/route.ts -- add Zod validation (line 57 uses raw req.json())
• src/app/profile/ or settings page -- add preferences UI
• src/configs/schema.ts -- reference usersTable fields (lines 17-18)
• src/inngest/functions.ts -- already respects preferences (lines 105-107)

Implementation Checklist

• Users can view and update notification preferences from their profile/settings
• Email notification toggle (enabled/disabled) is accessible
• Digest frequency (instant/daily/weekly/none) is selectable
• Preferences are persisted to the database correctly
• Notification sending respects updated preferences
• The preferences API route has Zod validation

Additional Context

This is a GSSoC'26 contributor issue created from the DoubtDesk market-readiness roadmap.

Field	Value
Level	intermediate
Area	notifications
Stack	Next.js, TypeScript, Drizzle, Neon Postgres, Clerk, Groq, Inngest

[DivyaShreeS09]

Hi @knoxiboy,

I would like to work on #520 (Add notification preferences for students and teachers).

I have reviewed the issue requirements and explored the codebase. I noticed that the preferences API, notification system, and related schema already exist, and I would like to extend them to implement the requested notification preference management features.

Could you please assign this issue to me?

Thank you.