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.config.ts

@@ -0,0 +1,14 @@
+// This file was generated by Prisma, and assumes you have installed the following:
+// npm install --save-dev prisma dotenv
+import "dotenv/config";
+import { defineConfig } from "prisma/config";
+
+export default defineConfig({
+  schema: "prisma/schema.prisma",
+  migrations: {
+    path: "prisma/migrations",
+  },
+  datasource: {
+    url: process.env["DATABASE_URL"],
+  },
+});