fix: assign project to round on creation (create ProjectRoundState)

- Add optional roundId field to project.create mutation input schema
- After project creation, update project.roundId FK and create a
  ProjectRoundState record (state: PENDING) when roundId is supplied
- Pass selectedRoundId from the new-project form to createProject.mutate()

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

src/app/(admin)/admin/projects/new/page.tsx

@@ -216,6 +216,7 @@ function NewProjectPageContent() {
 
     createProject.mutate({
       programId: selectedProgramId,
+      roundId: selectedRoundId || undefined,
       title: title.trim(),
       teamName: teamName.trim() || undefined,
       description: description.trim() || undefined,