Add Comment model for issue comments

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

prisma/migrations/20261001081829_comment/migration.sql

@@ -0,0 +1,25 @@
+-- CreateTable
+CREATE TABLE "comment" (
+    "id" TEXT NOT NULL,
+    "content" TEXT NOT NULL,
+    "issueId" INTEGER NOT NULL,
+    "authorId" TEXT,
+    "editedAt" TIMESTAMPTZ(3),
+    "deletedAt" TIMESTAMPTZ(3),
+    "createdAt" TIMESTAMPTZ(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" TIMESTAMPTZ(3) NOT NULL,
+
+    CONSTRAINT "comment_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE INDEX "comment_issueId_createdAt_idx" ON "comment"("issueId", "createdAt");
+
+-- CreateIndex
+CREATE INDEX "comment_authorId_idx" ON "comment"("authorId");
+
+-- AddForeignKey
+ALTER TABLE "comment" ADD CONSTRAINT "comment_issueId_fkey" FOREIGN KEY ("issueId") REFERENCES "issue"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "comment" ADD CONSTRAINT "comment_authorId_fkey" FOREIGN KEY ("authorId") REFERENCES "user"("id") ON DELETE SET NULL ON UPDATE CASCADE;