feat: add templates for transactional emails (#103)

* add template migration & router

* template CRUD

* templated transactional emails API

* zod schema fix & rearranging template columns

apps/web/prisma/migrations/20250207104036_add_template/migration.sql

@@ -0,0 +1,19 @@
+-- CreateTable
+CREATE TABLE "Template" (
+    "id" TEXT NOT NULL,
+    "name" TEXT NOT NULL,
+    "teamId" INTEGER NOT NULL,
+    "subject" TEXT NOT NULL,
+    "html" TEXT,
+    "content" TEXT,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" TIMESTAMP(3) NOT NULL,
+
+    CONSTRAINT "Template_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE INDEX "Template_createdAt_idx" ON "Template"("createdAt" DESC);
+
+-- AddForeignKey
+ALTER TABLE "Template" ADD CONSTRAINT "Template_teamId_fkey" FOREIGN KEY ("teamId") REFERENCES "Team"("id") ON DELETE CASCADE ON UPDATE CASCADE;