feat(admin): add instructor learning analytics and assessment management

New /api/admin routes: cohort learning summary (completion by stage, active learners),
per-student learning detail (attempts, hint usage, assessment history, capstone state),
scenario analytics (completion rate, avg attempts, failure/hint frequency, avg time), and a
needs-attention view (repeated failures, hints used but still stuck, inactivity, an expired
assessment - deliberately instructional wording, not punitive, with an explicit test asserting
that). Assessment definition CRUD (admin/owner only), cohort assignment and session view/cancel
(any instructor role, cohort-scoped for a plain instructor via the existing Phase 3A RBAC
helpers - no new authorization primitives needed).

New Learning and Assessments tabs in the admin portal, visible to every instructor role;
definition-authoring controls are shown but the server 403s a create/edit from a non-admin/
owner role, same pattern CohortsView already uses for admin-only controls.

frontend/src/admin/api.js

@@ -80,4 +80,18 @@ export const adminApi = {
   resetInstructorPassword: (id, new_password) => post(`/api/admin/instructors/${id}/reset-password`, { new_password }),
 
   auditEvents: () => get('/api/admin/audit-events'),
+
+  // ── Phase 3B: learning analytics ────────────────────────────────────────────────────────
+  cohortLearning: (id) => get(`/api/admin/cohorts/${id}/learning`),
+  studentLearning: (id) => get(`/api/admin/students/${id}/learning`),
+  scenarioAnalytics: (cohortId) => get(`/api/admin/scenario-analytics${cohortId ? `?cohort_id=${cohortId}` : ''}`),
+  needsAttention: (cohortId) => get(`/api/admin/cohorts/${cohortId}/needs-attention`),
+
+  // ── Phase 3B: assessment (exam + capstone) management ───────────────────────────────────
+  assessments: () => get('/api/admin/assessments'),
+  createAssessment: (fields) => post('/api/admin/assessments', fields),
+  updateAssessment: (id, fields) => patch(`/api/admin/assessments/${id}`, fields),
+  assignAssessment: (id, cohort_id) => post(`/api/admin/assessments/${id}/assign`, { cohort_id }),
+  assessmentSessions: (id) => get(`/api/admin/assessments/${id}/sessions`),
+  cancelAssessmentSession: (sessionId) => post(`/api/admin/assessment-sessions/${sessionId}/cancel`),
 }