Add missing migration for ProjectFile.pageCount column

Column was in Prisma schema but had no migration file, causing
'column does not exist' errors on file uploads.

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

prisma/migrations/20260216000000_add_projectfile_pagecount/migration.sql

@@ -0,0 +1,2 @@
+-- Add pageCount column to ProjectFile (was in schema but missing migration)
+ALTER TABLE "ProjectFile" ADD COLUMN IF NOT EXISTS "pageCount" INTEGER;