refactor: tech debt batch 2 — drop dead models, stale columns, schema cleanup

Schema:
- Drop 4 dead models: OverrideAction, NotificationPolicy, AssignmentException, AdvancementRule
- Drop 2 dead enums: OverrideReasonCode, AdvancementRuleType
- Drop 3 stale columns: Project.roundId, ConflictOfInterest.roundId, Evaluation.version
- Remove 3 back-relation fields from User, Assignment, Round

Code:
- Fix 6 COI queries in assignment.ts + 1 in juror-reassignment.ts
  (roundId filter → assignment.roundId after column drop)
- Remove orphaned Project.roundId write in project.ts createProject
- Remove advancementRules include from round.ts getById
- Remove AdvancementRule from RoundWithRelations type
- Clean up seed.ts (remove advancement rule seeding)
- Clean up tests/helpers.ts (remove dead model cleanup)
- Add TODO comments on user delete mutations (FK violation risk)

Migration: 20260308000000_drop_dead_models_and_stale_columns

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

tests/helpers.ts

@@ -329,7 +329,6 @@ export async function cleanupTestData(programId: string, userIds: string[] = [])
   // Delete in reverse dependency order — scoped by programId or userIds
   if (userIds.length > 0) {
     await prisma.decisionAuditLog.deleteMany({ where: { actorId: { in: userIds } } })
-    await prisma.overrideAction.deleteMany({ where: { actorId: { in: userIds } } })
     await prisma.auditLog.deleteMany({ where: { userId: { in: userIds } } })
   }
   // Competition/Round cascade cleanup
@@ -350,7 +349,6 @@ export async function cleanupTestData(programId: string, userIds: string[] = [])
   await prisma.evaluationSummary.deleteMany({ where: { round: { competition: { programId } } } })
   await prisma.evaluationDiscussion.deleteMany({ where: { round: { competition: { programId } } } })
   await prisma.projectRoundState.deleteMany({ where: { round: { competition: { programId } } } })
-  await prisma.advancementRule.deleteMany({ where: { round: { competition: { programId } } } })
   await prisma.awardEligibility.deleteMany({ where: { award: { program: { id: programId } } } })
   await prisma.awardVote.deleteMany({ where: { award: { program: { id: programId } } } })
   await prisma.awardJuror.deleteMany({ where: { award: { program: { id: programId } } } })