Expose user counts by education_level, occupation, learning_goal, and language_challange on GET /api/v1/analytics/dashboard.
Co-authored-by: Cursor <cursoragent@cursor.com>
Support all-time, year, year+month, and custom from/to query params with filtered metrics and time-series charts.
Co-authored-by: Cursor <cursoragent@cursor.com>
