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/(mentor)/mentor/page.tsx

@@ -149,18 +149,24 @@ export default function MentorDashboard() {
                       <div className="space-y-1">
                         <div className="flex items-center gap-2 text-sm text-muted-foreground">
                           <span>
-                            {project.round.program.year} Edition
+                            {project.program.year} Edition
                           </span>
-                          <span>•</span>
-                          <span>{project.round.name}</span>
+                          {project.roundProjects?.[0]?.round && (
+                            <>
+                              <span>•</span>
+                              <span>{project.roundProjects[0].round.name}</span>
+                            </>
+                          )}
                         </div>
                         <CardTitle className="flex items-center gap-2">
                           {project.title}
-                          <Badge
-                            variant={statusColors[project.status] || 'secondary'}
-                          >
-                            {project.status.replace('_', ' ')}
-                          </Badge>
+                          {project.roundProjects?.[0]?.status && (
+                            <Badge
+                              variant={statusColors[project.roundProjects[0].status] || 'secondary'}
+                            >
+                              {project.roundProjects[0].status.replace('_', ' ')}
+                            </Badge>
+                          )}
                         </CardTitle>
                         {project.teamName && (
                           <CardDescription>{project.teamName}</CardDescription>