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-candidatures.ts

@@ -321,7 +321,7 @@ async function main() {
       // Check if project already exists
       const existingProject = await prisma.project.findFirst({
         where: {
-          roundId: round.id,
+          programId: program.id,
           OR: [
             { title: projectName },
             { submittedByEmail: email },
@@ -365,10 +365,9 @@ async function main() {
       // Create project
       const project = await prisma.project.create({
         data: {
-          roundId: round.id,
+          programId: program.id,
           title: projectName,
           description: row['Comment ']?.trim() || null,
-          status: 'SUBMITTED',
           competitionCategory: mapCategory(row['Category']),
           oceanIssue: mapOceanIssue(row['Issue']),
           country: extractCountry(row['Country']),
@@ -392,6 +391,15 @@ async function main() {
         },
       })
 
+      // Create round-project association
+      await prisma.roundProject.create({
+        data: {
+          roundId: round.id,
+          projectId: project.id,
+          status: 'SUBMITTED',
+        },
+      })
+
       // Create team lead membership
       await prisma.teamMember.create({
         data: {
@@ -466,7 +474,7 @@ async function main() {
   console.log('\nBackfilling missing country codes...\n')
   let backfilled = 0
   const nullCountryProjects = await prisma.project.findMany({
-    where: { roundId: round.id, country: null },
+    where: { programId: program.id, country: null },
     select: { id: true, submittedByEmail: true, title: true },
   })