Fix round deletion FK constraint with migration and defensive code

- Add SQL migration to CASCADE Evaluation.formId and SET NULL ProjectFile.roundId
- Explicitly delete evaluations in round delete transaction as defensive measure
- Make sidebar Apply Page link dynamic using current edition context

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/server/routers/round.ts

@@ -615,6 +615,12 @@ export const roundRouter = router({
           userAgent: ctx.userAgent,
         })
 
+        // Delete evaluations first to avoid FK constraint on Evaluation.formId
+        // (formId FK may not have CASCADE in older DB schemas)
+        await tx.evaluation.deleteMany({
+          where: { form: { roundId: input.id } },
+        })
+
         await tx.round.delete({
           where: { id: input.id },
         })