feat: add prediction note, admin role update, trending markets & competition participants endpoints

[Akanimoh12]

Summary

This PR implements four new backend endpoints addressing multiple open issues:

Closes #443
Closes #403
Closes #431
Closes #424

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Issue #443 — [Backend] Prediction History - Edit Prediction Note

Endpoint: PATCH /predictions/:id/note

Changes:

• Added note field (text, nullable) to the Prediction entity
• Created UpdatePredictionNoteDto with validation (string, max 1000 chars)
• Implemented updateNote() in PredictionsService with ownership validation — only the prediction owner can update their note
• Added PATCH :id/note endpoint in PredictionsController with ParseUUIDPipe
• Included note field in PredictionWithStatus interface and enrichWithStatus() response
• Created database migration 1775000000000-AddPredictionNoteColumn
• Added unit tests for successful note update and ownership validation (NotFoundException)

Access: Authenticated users (own predictions only)

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Issue #403 — [Backend] Admin User Management - Update User Role

Endpoint: PATCH /admin/users/:id/role

Changes:

• Created UpdateUserRoleDto with @IsEnum(Role) validation (user | admin)
• Implemented updateUserRole() in AdminService with:
  • Self-demotion prevention (BadRequestException if admin tries to change own role)
  • User existence validation
  • Audit logging via AnalyticsService.logActivity() with previous/new role details
• Added PATCH users/:id/role endpoint in AdminController (protected by @Roles(Role.Admin) guard)
• Added unit tests for role update, self-demotion prevention, and user not found scenarios

Access: Admin only
Validation: Cannot demote yourself

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Issue #431 — [Backend] Market Discovery - Trending Markets

Endpoint: GET /markets/trending

Changes:

• Created TrendingMarketsQueryDto with pagination support (page/limit, max 50)
• Created TrendingMarketItem and PaginatedTrendingMarketsResponse DTOs
• Implemented trending algorithm in MarketsService with scoring based on:
  • Participant count (50% weight) — higher participation = more trending
  • Pool size (30% weight) — larger stakes = more activity
  • Time to resolution (20% weight) — markets ending sooner rank higher
• Added in-memory caching with 15-minute TTL to avoid expensive recalculations
• Route placed before :id parameterized routes to avoid path conflicts
• Added unit tests for trending score sorting, pagination, and cache behavior

Access: Public

---

Issue #424 — [Backend] Competition - Get Participants

Endpoint: GET /competitions/:id/participants

Changes:

• Created ListParticipantsQueryDto with pagination support (page/limit, max 50)
• Created ParticipantItem and PaginatedParticipantsResponse DTOs
• Implemented getParticipants() in CompetitionsService with:
  • Competition existence validation
  • Join with User entity for username/address display
  • Ordered by score (DESC) then join date (ASC) for rankings
• Added CompetitionParticipant entity to CompetitionsModule imports
• Added GET :id/participants endpoint in CompetitionsController (Public)
• Added unit tests for paginated participants and competition not found scenarios

Access: Public

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Testing

All existing and new tests pass:

• 30 test suites, 194 tests — all passing
• Lint — clean (ESLint with TypeScript strict checks)
• Build — successful compilation

Files Changed

Area	Files
Predictions	prediction.entity.ts, predictions.controller.ts, predictions.service.ts, list-my-predictions.dto.ts, update-prediction-note.dto.ts, predictions.service.spec.ts
Admin	admin.controller.ts, admin.service.ts, update-user-role.dto.ts, admin.service.spec.ts
Markets	markets.controller.ts, markets.service.ts, trending-markets.dto.ts, markets.service.spec.ts
Competitions	competitions.controller.ts, competitions.service.ts, competitions.module.ts, list-participants.dto.ts, competitions.service.spec.ts
Migrations	1775000000000-AddPredictionNoteColumn.ts

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Project	Deployment	Actions	Updated (UTC)
insight-arena-4rll	Ready	Preview, Comment	Mar 30, 2026 0:10am

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