FAC-144 feat: expose faculty profilePicture on faculty report DTO

[y4nder]

Summary

The analytics ReportFacultyDto only exposes id and name. The faculty analytics / faculty report UI renders the faculty's name as the page title but has no visual identifier, and the frontend has no way to show the faculty's profile picture on that screen today.

The user entity already carries user_profile_picture (synced from Moodle and already exposed on FacultyShortResponseDto used by enrollments), so the data is available — it just isn't surfaced on the analytics report DTO.

Scope

• Add optional profilePicture to ReportFacultyDto.
• Update AnalyticsService.BuildFacultyReportData to select u.user_profile_picture alongside name and include it on the returned faculty DTO.
• Treat empty strings as null (user_profile_picture || null).

Acceptance Criteria

• GET /analytics/faculty/:id/report response includes faculty.profilePicture (nullable string).
• All existing unit tests still pass (npm run verify).
• No DB migration required — the column already exists.

Out of Scope

• Upload / edit flows for profile pictures.
• Changes to the app (tracked separately under the web ticket).