feat: prisma schema User + SyncRun + seed admin

Sets up Prisma 7 with SQLite (better-sqlite3 adapter), User and SyncRun models, migration, and admin seed account for mathieu.fort@gmail.com.

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

prisma/schema.prisma

@@ -0,0 +1,30 @@
+generator client {
+  provider = "prisma-client-js"
+}
+
+datasource db {
+  provider = "sqlite"
+}
+
+model User {
+  id        String    @id @default(cuid())
+  email     String    @unique
+  name      String
+  password  String
+  role      String    @default("gestionnaire")
+  createdAt DateTime  @default(now())
+  syncRuns  SyncRun[]
+}
+
+model SyncRun {
+  id          String   @id @default(cuid())
+  createdAt   DateTime @default(now())
+  userId      String
+  user        User     @relation(fields: [userId], references: [id])
+  status      String
+  created     Int      @default(0)
+  updated     Int      @default(0)
+  deactivated Int      @default(0)
+  errors      Int      @default(0)
+  log         String   @default("[]")
+}