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>

prisma/seed-jury-demo.ts

@@ -64,13 +64,14 @@ async function main() {
 
   console.log(`Voting window: ${votingStart.toISOString()} → ${votingEnd.toISOString()}\n`)
 
-  // Get some projects to assign
-  const projects = await prisma.project.findMany({
+  // Get some projects to assign (via RoundProject)
+  const roundProjects = await prisma.roundProject.findMany({
     where: { roundId: round.id },
     take: 8,
-    orderBy: { createdAt: 'desc' },
-    select: { id: true, title: true },
+    orderBy: { addedAt: 'desc' },
+    select: { project: { select: { id: true, title: true } } },
   })
+  const projects = roundProjects.map(rp => rp.project)
 
   if (projects.length === 0) {
     console.error('No projects found! Run seed-candidatures first.')