feat(01-01): add RankingSnapshot model + enums to schema.prisma

- Add RankingTriggerType enum (MANUAL, AUTO, RETROACTIVE, QUICK)
- Add RankingMode enum (PREVIEW, CONFIRMED, QUICK)
- Add RankingSnapshotStatus enum (PENDING, RUNNING, COMPLETED, FAILED)
- Add RankingSnapshot model with roundId/triggeredById FKs, criteria/results JSON fields, AI metadata
- Add Round.rankingSnapshots back-relation (RoundRankingSnapshots)
- Add User.rankingSnapshots back-relation (TriggeredRankingSnapshots)
- Create migration 20260227000000_add_ranking_snapshot
- Regenerate Prisma client (prisma.rankingSnapshot accessible)

prisma/schema.prisma

@@ -425,6 +425,9 @@ model User {
   submissionPromotions              SubmissionPromotionEvent[] @relation("SubmissionPromoter")
   deliberationReplacements          DeliberationParticipant[]  @relation("DeliberationReplacement")
 
+  // AI Ranking
+  rankingSnapshots                  RankingSnapshot[]          @relation("TriggeredRankingSnapshots")
+
   @@index([role])
   @@index([status])
 }
@@ -1405,6 +1408,74 @@ enum AssignmentJobStatus {
   FAILED
 }
 
+// =============================================================================
+// AI RANKING MODELS
+// =============================================================================
+
+enum RankingTriggerType {
+  MANUAL      // Admin clicked "Run ranking"
+  AUTO        // Auto-triggered by assignment completion
+  RETROACTIVE // Retroactive scan on deployment
+  QUICK       // Quick-rank mode (no preview)
+}
+
+enum RankingMode {
+  PREVIEW   // Parsed rules shown to admin (not yet applied)
+  CONFIRMED // Admin confirmed rules, ranking applied
+  QUICK     // Quick-rank: parse + apply without preview
+}
+
+enum RankingSnapshotStatus {
+  PENDING
+  RUNNING
+  COMPLETED
+  FAILED
+}
+
+// Captures a point-in-time AI ranking run for a round
+model RankingSnapshot {
+  id String @id @default(cuid())
+
+  roundId String
+
+  // Trigger metadata
+  triggeredById String?            // null = auto-triggered
+  triggerType   RankingTriggerType @default(MANUAL)
+
+  // Criteria used
+  criteriaText    String @db.Text
+  parsedRulesJson Json   @db.JsonB
+
+  // Results per category (either can be null/empty if no projects in that category)
+  startupRankingJson Json? @db.JsonB
+  conceptRankingJson Json? @db.JsonB
+
+  // Evaluation data freeze (raw scores at time of ranking)
+  evaluationDataJson Json? @db.JsonB
+
+  // Mode and status
+  mode   RankingMode           @default(PREVIEW)
+  status RankingSnapshotStatus @default(COMPLETED)
+
+  // Post-drag-and-drop reorders (Phase 2 will populate this)
+  reordersJson Json? @db.JsonB
+
+  // AI metadata
+  model      String?
+  tokensUsed Int     @default(0)
+
+  createdAt DateTime @default(now())
+  updatedAt DateTime @updatedAt
+
+  // Relations
+  round       Round @relation("RoundRankingSnapshots", fields: [roundId], references: [id], onDelete: Cascade)
+  triggeredBy User? @relation("TriggeredRankingSnapshots", fields: [triggeredById], references: [id], onDelete: SetNull)
+
+  @@index([roundId])
+  @@index([triggeredById])
+  @@index([createdAt])
+}
+
 // Tracks progress of long-running AI tagging jobs
 model TaggingJob {
   id             String           @id @default(cuid())
@@ -2146,6 +2217,7 @@ model Round {
   filteringResults      FilteringResult[]
   filteringJobs         FilteringJob[]
   assignmentJobs        AssignmentJob[]
+  rankingSnapshots      RankingSnapshot[]    @relation("RoundRankingSnapshots")
   reminderLogs          ReminderLog[]
   evaluationSummaries   EvaluationSummary[]
   evaluationDiscussions EvaluationDiscussion[]