Fix Task 1 schema.prisma for exact DDL fidelity and drop --force

Review of Task 1 (d86245a) found two issues:

1. prisma/schema.prisma didn't reproduce db/schema.sql's DDL exactly.
   Add @db.DateTime(0) to createdAt/updatedAt/expiresAt/cleanedAt (Prisma
   otherwise defaults to DATETIME(3)), and explicit map: names on the
   uuid unique constraint and status/expiresAt indexes so they match the
   real table's uniq_uuid/idx_status/idx_expires_at. Verified via
   `prisma migrate diff --from-empty --to-schema-datamodel`, which now
   shows DATETIME(0)/CURRENT_TIMESTAMP(0) and the correct names. Table
   collation and updated_at's ON UPDATE CURRENT_TIMESTAMP remain
   documented, accepted gaps with no schema-level fix in Prisma's mysql
   provider.

2. The original @prisma/client@6/prisma@6 pin used --force without
   diagnosing why. Reinstalled with `npm install @prisma/client@6
   prisma@6 --save-dev` (no --force) directly against this project's
   node_modules: it completed cleanly with no conflicts, confirming
   --force was unnecessary.

`prisma validate`, `prisma generate`, and the full test suite
(69 passed, 4 pre-existing failures unrelated to this change) all pass.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

prisma/schema.prisma

@@ -16,7 +16,7 @@ enum JobStatus {
 
 model ConversionJob {
   id                        Int       @id @default(autoincrement()) @db.UnsignedInt
-  uuid                      String    @unique @db.Char(36)
+  uuid                      String    @unique(map: "uniq_uuid") @db.Char(36)
   status                    JobStatus @default(pending)
   family                    String    @db.VarChar(32)
   sourceFormat              String    @map("source_format") @db.VarChar(16)
@@ -32,12 +32,12 @@ model ConversionJob {
   conversionDurationSeconds Decimal?  @map("conversion_duration_seconds") @db.Decimal(10, 3)
   errorMessage              String?   @map("error_message") @db.VarChar(255)
   errorLog                  String?   @map("error_log") @db.Text
-  createdAt                  DateTime  @default(now()) @map("created_at")
+  createdAt                 DateTime  @default(now()) @map("created_at") @db.DateTime(0)
-  updatedAt                  DateTime  @default(now()) @updatedAt @map("updated_at")
+  updatedAt                 DateTime  @default(now()) @updatedAt @map("updated_at") @db.DateTime(0)
-  expiresAt                  DateTime  @map("expires_at")
+  expiresAt                 DateTime  @map("expires_at") @db.DateTime(0)
-  cleanedAt                  DateTime? @map("cleaned_at")
+  cleanedAt                 DateTime? @map("cleaned_at") @db.DateTime(0)
 
-  @@index([status])
+  @@index([status], map: "idx_status")
-  @@index([expiresAt])
+  @@index([expiresAt], map: "idx_expires_at")
   @@map("conversion_jobs")
 }