refactor: tech debt batch 3 — type safety + assignment router split

#5 — Replaced 55x PrismaClient | any with proper Prisma types across 8 files
- Service files: PrismaClient | any → PrismaClient, tx: any → Prisma.TransactionClient
- Fixed 4 real bugs uncovered by typing:
  - mentor-workspace.ts: wrong FK fields (mentorAssignmentId → workspaceId, role → senderRole)
  - ai-shortlist.ts: untyped string passed to CompetitionCategory enum filter
  - result-lock.ts: unknown passed where Prisma.InputJsonValue required

#9 — Split assignment.ts (2,775 lines) into 6 focused files:
  - shared.ts (93 lines) — MOVABLE_EVAL_STATUSES, buildBatchNotifications, getCandidateJurors
  - assignment-crud.ts (473 lines) — 8 core CRUD procedures
  - assignment-suggestions.ts (880 lines) — AI suggestions + job runner
  - assignment-notifications.ts (138 lines) — 2 notification procedures
  - assignment-redistribution.ts (1,162 lines) — 8 reassign/transfer procedures
  - index.ts (15 lines) — barrel export with router merge, zero frontend changes

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

src/server/services/submission-manager.ts

@@ -34,7 +34,7 @@ export type SubmissionValidationResult = {
 export async function openWindow(
   windowId: string,
   actorId: string,
-  prisma: PrismaClient | any,
+  prisma: PrismaClient,
 ): Promise<WindowLifecycleResult> {
   try {
     const window = await prisma.submissionWindow.findUnique({ where: { id: windowId } })
@@ -47,7 +47,7 @@ export async function openWindow(
       return { success: false, errors: ['Cannot open a locked window'] }
     }
 
-    await prisma.$transaction(async (tx: any) => {
+    await prisma.$transaction(async (tx: Prisma.TransactionClient) => {
       await tx.submissionWindow.update({
         where: { id: windowId },
         data: {
@@ -93,7 +93,7 @@ export async function openWindow(
 export async function closeWindow(
   windowId: string,
   actorId: string,
-  prisma: PrismaClient | any,
+  prisma: PrismaClient,
 ): Promise<WindowLifecycleResult> {
   try {
     const window = await prisma.submissionWindow.findUnique({ where: { id: windowId } })
@@ -102,7 +102,7 @@ export async function closeWindow(
       return { success: false, errors: [`Submission window ${windowId} not found`] }
     }
 
-    await prisma.$transaction(async (tx: any) => {
+    await prisma.$transaction(async (tx: Prisma.TransactionClient) => {
       const data: Record<string, unknown> = {
         windowCloseAt: new Date(),
       }
@@ -155,7 +155,7 @@ export async function closeWindow(
 export async function lockWindow(
   windowId: string,
   actorId: string,
-  prisma: PrismaClient | any,
+  prisma: PrismaClient,
 ): Promise<WindowLifecycleResult> {
   try {
     const window = await prisma.submissionWindow.findUnique({ where: { id: windowId } })
@@ -168,7 +168,7 @@ export async function lockWindow(
       return { success: false, errors: ['Window is already locked'] }
     }
 
-    await prisma.$transaction(async (tx: any) => {
+    await prisma.$transaction(async (tx: Prisma.TransactionClient) => {
       await tx.submissionWindow.update({
         where: { id: windowId },
         data: { isLocked: true },
@@ -212,7 +212,7 @@ export async function lockWindow(
  */
 export async function checkDeadlinePolicy(
   windowId: string,
-  prisma: PrismaClient | any,
+  prisma: PrismaClient,
 ): Promise<DeadlineStatus> {
   const window = await prisma.submissionWindow.findUnique({ where: { id: windowId } })
 
@@ -273,7 +273,7 @@ export async function validateSubmission(
   projectId: string,
   windowId: string,
   files: Array<{ mimeType: string; size: number; requirementId?: string }>,
-  prisma: PrismaClient | any,
+  prisma: PrismaClient,
 ): Promise<SubmissionValidationResult> {
   const errors: string[] = []
 
@@ -327,7 +327,7 @@ export async function validateSubmission(
  */
 export async function isWindowReadOnly(
   windowId: string,
-  prisma: PrismaClient | any,
+  prisma: PrismaClient,
 ): Promise<boolean> {
   const status = await checkDeadlinePolicy(windowId, prisma)
   return status.status === 'LOCKED' || status.status === 'CLOSED'
@@ -340,7 +340,7 @@ export async function isWindowReadOnly(
  */
 export async function getVisibleWindows(
   roundId: string,
-  prisma: PrismaClient | any,
+  prisma: PrismaClient,
 ) {
   const visibility = await prisma.roundSubmissionVisibility.findMany({
     where: { roundId, canView: true },