feat: implement message CRUD and dark mode

- Add Message, Recipient models and migration
- Create message API routes (GET, POST, PATCH, DELETE)
- Fix IDOR vulnerability in PATCH (verify ownership before delete)
- Add dashboard and message pages (list, new, detail)
- Add UI components (card, input, label, textarea)
- Enable dark mode in layout
- Add session user id typing to NextAuth
- Add AGENTS.md memory bank documentation

prisma/migrations/20251224113949_add_message_models/migration.sql

@@ -0,0 +1,42 @@
+-- CreateTable
+CREATE TABLE "Message" (
+    "id" TEXT NOT NULL,
+    "userId" TEXT NOT NULL,
+    "title" TEXT NOT NULL,
+    "content" TEXT,
+    "status" TEXT NOT NULL DEFAULT 'DRAFT',
+    "lastPing" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "checkInterval" INTEGER NOT NULL DEFAULT 24,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" TIMESTAMP(3) NOT NULL,
+
+    CONSTRAINT "Message_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateTable
+CREATE TABLE "Recipient" (
+    "id" TEXT NOT NULL,
+    "messageId" TEXT NOT NULL,
+    "email" TEXT NOT NULL,
+
+    CONSTRAINT "Recipient_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateTable
+CREATE TABLE "Attachment" (
+    "id" TEXT NOT NULL,
+    "messageId" TEXT NOT NULL,
+    "fileUrl" TEXT NOT NULL,
+    "fileName" TEXT NOT NULL,
+
+    CONSTRAINT "Attachment_pkey" PRIMARY KEY ("id")
+);
+
+-- AddForeignKey
+ALTER TABLE "Message" ADD CONSTRAINT "Message_userId_fkey" FOREIGN KEY ("userId") REFERENCES "User"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "Recipient" ADD CONSTRAINT "Recipient_messageId_fkey" FOREIGN KEY ("messageId") REFERENCES "Message"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "Attachment" ADD CONSTRAINT "Attachment_messageId_fkey" FOREIGN KEY ("messageId") REFERENCES "Message"("id") ON DELETE CASCADE ON UPDATE CASCADE;