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/server/routers/assignment.ts

@@ -286,12 +286,16 @@ export const assignmentRouter = router({
           where: { roundId: input.roundId },
           _count: true,
         }),
-        ctx.prisma.project.findMany({
+        ctx.prisma.roundProject.findMany({
           where: { roundId: input.roundId },
-          select: {
-            id: true,
-            title: true,
-            _count: { select: { assignments: true } },
+          include: {
+            project: {
+              select: {
+                id: true,
+                title: true,
+                _count: { select: { assignments: true } },
+              },
+            },
           },
         }),
       ])
@@ -302,7 +306,7 @@ export const assignmentRouter = router({
       })
 
       const projectsWithFullCoverage = projectCoverage.filter(
-        (p) => p._count.assignments >= round.requiredReviews
+        (rp) => rp.project._count.assignments >= round.requiredReviews
       ).length
 
       return {
@@ -354,15 +358,20 @@ export const assignmentRouter = router({
       })
 
       // Get all projects that need more assignments
-      const projects = await ctx.prisma.project.findMany({
+      const roundProjectEntries = await ctx.prisma.roundProject.findMany({
         where: { roundId: input.roundId },
-        select: {
-          id: true,
-          title: true,
-          tags: true,
-          _count: { select: { assignments: true } },
+        include: {
+          project: {
+            select: {
+              id: true,
+              title: true,
+              tags: true,
+              _count: { select: { assignments: true } },
+            },
+          },
         },
       })
+      const projects = roundProjectEntries.map((rp) => rp.project)
 
       // Get existing assignments to avoid duplicates
       const existingAssignments = await ctx.prisma.assignment.findMany({
@@ -482,17 +491,22 @@ export const assignmentRouter = router({
       })
 
       // Get all projects in the round
-      const projects = await ctx.prisma.project.findMany({
+      const roundProjectEntries = await ctx.prisma.roundProject.findMany({
         where: { roundId: input.roundId },
-        select: {
-          id: true,
-          title: true,
-          description: true,
-          tags: true,
-          teamName: true,
-          _count: { select: { assignments: true } },
+        include: {
+          project: {
+            select: {
+              id: true,
+              title: true,
+              description: true,
+              tags: true,
+              teamName: true,
+              _count: { select: { assignments: true } },
+            },
+          },
         },
       })
+      const projects = roundProjectEntries.map((rp) => rp.project)
 
       // Get existing assignments
       const existingAssignments = await ctx.prisma.assignment.findMany({