feat:Notifications: preferences, unread count, and tip/goal triggers

[Samuel1505]

Notifications: preferences, unread count, and tip/goal triggers

Closes #963,
closes #964,
closes #966,
closes #967

Summary

Implements the four open notifications issues on top of the existing
list/get/mark-read module:

• Notifications: Notification preferences model + endpoint #967 — Notification preferences model + endpoint. New
  NotificationPreference model (tipReceived / goalReached booleans,
  default true) with GET and PATCH /api/v1/notifications/preferences.
  A missing row is treated as all-enabled, so existing users don't need a
  backfill.
• Notifications: Unread count endpoint #966 — Unread count endpoint. GET /api/v1/notifications/unread-count
  returns { count } for the caller's unread, non-deleted notifications.
• Notifications: Notify creator on new tip #963 — Notify creator on new tip. recordTip now calls the new
  createNotification helper once a tip is newly inserted (not on the
  existing-tip or P2002 dedupe paths). Skips self-tips and recipients with
  no off-chain User row; a notification failure is logged and never blocks
  the tip response.
• Notifications: Notify on goal reached #964 — Notify on goal reached. The indexer's projectGoalReached
  projection notifies the creator the moment a Goal transitions into
  COMPLETED. The transition is detected from the row's prior status (not
  from event-replay bookkeeping), so replaying the same ledger never creates
  a duplicate notification.

createNotification is the shared piece: it persists the Notification row,
checks the caller's preference for that type, and broadcasts over the
existing Socket.IO realtime gateway (emitNotificationCreated) — the same
mechanism already used for tip.created.

Also fixed (blocking, unrelated to the four issues above)

The branch had several unresolved-merge artifacts that broke the build
outright — prisma generate and tsc both failed before any of this work
could be verified:

• prisma/schema.prisma: the User model had every relation field listed
  twice, and TipStatus was declared as two conflicting enums.
• src/app.ts: two import blocks were concatenated mid-statement (} on its
  own line) and several routers were mounted twice.
• src/common/errors/AppError.ts: ServiceUnavailableError was declared
  twice (duplicate identifier).
• src/modules/x/x.test.ts: a pre-existing tsc error from an unsafe
  globalThis cast (one-line fix, unknown intermediate cast).

These are isolated in their own fix: commit so they're easy to review or
drop separately.

Verification

npm run typecheck   # passes
npm run lint         # passes (0 errors, 6 pre-existing `any` warnings, untouched)
npm run test         # no new failures; 47 pre-existing failures unchanged

The sandbox this was built in has no Docker/Postgres/Redis available, so the
suites that need a live database (tests/*.test.ts integration tests via
resetDb, and src/modules/x/x.test.ts's real-prisma cases) fail exactly as
they did before this change — confirmed by diffing the failing-test list
before and after. All new notification behavior is covered by
mocked-Prisma unit/integration tests (vitest + supertest), matching the
existing pattern in notifications.test.ts, and passes locally. Please
re-run the full suite with docker compose -f backend/docker-compose.yml up -d before merging to confirm the DB-backed suites are unaffected.

New migration

prisma/migrations/20260725033000_add_notification_preference/ — creates
NotificationPreference (unique userId, FK to User with cascade
delete).

Test plan

• npm run typecheck
• npm run lint
• npm run test (mocked unit/integration suites; DB-backed suites
  unverifiable in this sandbox, see above)
• Re-run npm run test with Postgres + Redis up to confirm DB-backed
  suites still pass
• Manual check: GET/PATCH /api/v1/notifications/preferences,
  GET /api/v1/notifications/unread-count

[drips-wave]

@Samuel1505 Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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[Akanimoh12]

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