Make all migration SQL files idempotent for clean prod deploys

Added IF NOT EXISTS, IF EXISTS, and DO $$ EXCEPTION guards to all
migration files from 20260205 onwards so they survive partial application
and work correctly on both fresh databases and existing deployments.

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

prisma/migrations/20260215100000_add_self_service_fields/migration.sql

@@ -1,3 +1,7 @@
 -- AlterTable
-ALTER TABLE "JuryGroupMember" ADD COLUMN "selfServiceCap" INTEGER,
-ADD COLUMN "selfServiceRatio" DOUBLE PRECISION;
+DO $$ BEGIN
+    ALTER TABLE "JuryGroupMember" ADD COLUMN "selfServiceCap" INTEGER;
+EXCEPTION WHEN duplicate_column THEN NULL; END $$;
+DO $$ BEGIN
+    ALTER TABLE "JuryGroupMember" ADD COLUMN "selfServiceRatio" DOUBLE PRECISION;
+EXCEPTION WHEN duplicate_column THEN NULL; END $$;