Add initial Prisma migration

prisma migrate deploy requires migration files to exist — creates the
users, folders, and connections tables with all foreign key constraints.

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

backend/prisma/migrations/20240101000000_init/migration.sql

@@ -0,0 +1,59 @@
+-- CreateTable
+CREATE TABLE "users" (
+    "id" TEXT NOT NULL,
+    "username" TEXT NOT NULL,
+    "passwordHash" TEXT NOT NULL,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+
+    CONSTRAINT "users_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateTable
+CREATE TABLE "folders" (
+    "id" TEXT NOT NULL,
+    "name" TEXT NOT NULL,
+    "parentId" TEXT,
+    "userId" TEXT NOT NULL,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+
+    CONSTRAINT "folders_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateTable
+CREATE TABLE "connections" (
+    "id" TEXT NOT NULL,
+    "name" TEXT NOT NULL,
+    "host" TEXT NOT NULL,
+    "port" INTEGER NOT NULL,
+    "protocol" TEXT NOT NULL,
+    "username" TEXT NOT NULL,
+    "encryptedPassword" TEXT,
+    "privateKey" TEXT,
+    "domain" TEXT,
+    "osType" TEXT,
+    "notes" TEXT,
+    "folderId" TEXT,
+    "userId" TEXT NOT NULL,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+
+    CONSTRAINT "connections_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE UNIQUE INDEX "users_username_key" ON "users"("username");
+
+-- AddForeignKey
+ALTER TABLE "folders" ADD CONSTRAINT "folders_parentId_fkey"
+    FOREIGN KEY ("parentId") REFERENCES "folders"("id") ON DELETE SET NULL ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "folders" ADD CONSTRAINT "folders_userId_fkey"
+    FOREIGN KEY ("userId") REFERENCES "users"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "connections" ADD CONSTRAINT "connections_folderId_fkey"
+    FOREIGN KEY ("folderId") REFERENCES "folders"("id") ON DELETE SET NULL ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "connections" ADD CONSTRAINT "connections_userId_fkey"
+    FOREIGN KEY ("userId") REFERENCES "users"("id") ON DELETE CASCADE ON UPDATE CASCADE;