Switch Prisma from SQLite to PostgreSQL for production deploy.

Co-authored-by: Cursor <cursoragent@cursor.com>

prisma/schema.prisma

@@ -3,8 +3,8 @@ generator client {
 }
 
 datasource db {
-  // Local scaffold default: SQLite. For MySQL set provider = "mysql" and DATABASE_URL accordingly.
-  provider = "sqlite"
+  // Production + shared host: PostgreSQL. Local: Docker Postgres or same server DB.
+  provider = "postgresql"
   url      = env("DATABASE_URL")
 }