Decouple projects from rounds with RoundProject join table

Projects now exist at the program level instead of being locked to a
single round. A new RoundProject join table enables many-to-many
relationships with per-round status tracking. Rounds have sortOrder
for configurable progression paths.

- Add RoundProject model, programId on Project, sortOrder on Round
- Migration preserves existing data (roundId -> RoundProject entries)
- Update all routers to query through RoundProject join
- Add assign/remove/advance/reorder round endpoints
- Add Assign, Advance, Remove Projects dialogs on round detail page
- Add round reorder controls (up/down arrows) on rounds list
- Show all rounds on project detail page

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/app/(admin)/admin/programs/[id]/page.tsx

@@ -138,7 +138,7 @@ export default async function ProgramDetailPage({ params }: ProgramDetailPagePro
                         {round.status}
                       </Badge>
                     </TableCell>
-                    <TableCell>{round._count.projects}</TableCell>
+                    <TableCell>{round._count.roundProjects}</TableCell>
                     <TableCell>{round._count.assignments}</TableCell>
                     <TableCell>{formatDateOnly(round.createdAt)}</TableCell>
                   </TableRow>