Add jury assignment transfer, cap redistribution, and learning hub overhaul

- Add getTransferCandidates/transferAssignments procedures for targeted
  assignment moves between jurors with TOCTOU guards and audit logging
- Add getOverCapPreview/redistributeOverCap for auto-redistributing
  assignments when a juror's cap is lowered below their current load
- Add TransferAssignmentsDialog (2-step: select projects, pick destinations)
- Extend InlineMemberCap with over-cap detection and redistribute banner
- Extend getReassignmentHistory to show ASSIGNMENT_TRANSFER and CAP_REDISTRIBUTE events
- Learning hub: replace ResourceType/CohortLevel enums with accessJson JSONB,
  add coverImageKey, resource detail pages for jury/mentor, shared renderer
- Migration: 20260221200000_learning_hub_overhaul

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

prisma/schema.prisma

@@ -115,19 +115,6 @@ enum NotificationChannel {
   NONE
 }
 
-enum ResourceType {
-  PDF
-  VIDEO
-  DOCUMENT
-  LINK
-  OTHER
-}
-
-enum CohortLevel {
-  ALL
-  SEMIFINALIST
-  FINALIST
-}
 
 enum PartnerVisibility {
   ADMIN_ONLY
@@ -1010,13 +997,12 @@ model NotificationEmailSetting {
 // =============================================================================
 
 model LearningResource {
-  id           String       @id @default(cuid())
+  id           String  @id @default(cuid())
   programId    String? // null = global resource
   title        String
-  description  String?      @db.Text
-  contentJson  Json?        @db.JsonB // BlockNote document structure
-  resourceType ResourceType
-  cohortLevel  CohortLevel  @default(ALL)
+  description  String? @db.Text
+  contentJson  Json?   @db.JsonB // BlockNote document structure
+  accessJson   Json?   @db.JsonB // Fine-grained access rules
 
   // File storage (for uploaded resources)
   fileName  String?
@@ -1025,6 +1011,9 @@ model LearningResource {
   bucket    String?
   objectKey String?
 
+  // Cover image (stored in MinIO)
+  coverImageKey String?
+
   // External link
   externalUrl String?
 
@@ -1041,7 +1030,6 @@ model LearningResource {
   accessLogs ResourceAccess[]
 
   @@index([programId])
-  @@index([cohortLevel])
   @@index([isPublished])
   @@index([sortOrder])
 }