feat: setup the attachment to the passenger api

apps/edr-passenger-api/prisma/migrations/20260717090000_support_chat_attachments/migration.sql

@@ -0,0 +1,39 @@
+-- Support chat attachments.
+--
+-- `SupportMessage.text` becomes nullable so an attachment-only message can say
+-- "there is no text" instead of smuggling that through an empty string. This is
+-- a catalog-only change in Postgres — no table rewrite, no long lock.
+ALTER TABLE "SupportMessage" ALTER COLUMN "text" DROP NOT NULL;
+
+-- The `attachments` JSONB column has been dead since the init migration: never
+-- written, never read, absent from every DTO. It is dropped rather than reused —
+-- an untyped blob gives no file identity, no size accounting, and nothing to
+-- cascade on delete. Real rows replace it below. (The name is also needed for
+-- the new relation.)
+ALTER TABLE "SupportMessage" DROP COLUMN "attachments";
+
+-- Backs keyset pagination of a thread (newest-first over (createdAt, id)).
+-- Without it, paging a long thread degrades to a scan per page.
+-- CreateIndex
+CREATE INDEX "SupportMessage_conversationId_createdAt_idx" ON "SupportMessage"("conversationId", "createdAt");
+
+-- CreateTable
+CREATE TABLE "SupportAttachment" (
+    "id" TEXT NOT NULL,
+    "messageId" TEXT NOT NULL,
+    "name" TEXT NOT NULL,
+    "mimeType" TEXT NOT NULL,
+    "size" INTEGER NOT NULL,
+    "url" TEXT NOT NULL,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+
+    CONSTRAINT "SupportAttachment_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE INDEX "SupportAttachment_messageId_idx" ON "SupportAttachment"("messageId");
+
+-- AddForeignKey
+-- CASCADE: an attachment has no meaning without its message. (Object bytes in
+-- MinIO are not reaped by this — deleting messages is not a flow that exists.)
+ALTER TABLE "SupportAttachment" ADD CONSTRAINT "SupportAttachment_messageId_fkey" FOREIGN KEY ("messageId") REFERENCES "SupportMessage"("id") ON DELETE CASCADE ON UPDATE CASCADE;

apps/edr-passenger-api/prisma/schema.prisma

@@ -916,10 +916,37 @@ model SupportMessage {
   id             String              @id @default(uuid())
   conversationId String
   sender         SupportSender
-  text           String
-  attachments    Json?
+  /// NULL for an attachment-only message — absence of text is representable
+  /// rather than smuggled through "". The DTO maps NULL -> "".
+  text           String?
   createdAt      DateTime            @default(now())
   conversation   SupportConversation @relation(fields: [conversationId], references: [id])
+  attachments    SupportAttachment[]
+  /// Backs keyset pagination of a thread (newest-first over (createdAt, id)).
+  /// Without it, paging a long thread degrades to a scan per page.
+  @@index([conversationId, createdAt])
+  @@schema("passenger")
+}
+
+/// A file posted on a support message.
+///
+/// The freight side stores the equivalent in its polymorphic `freight.files`
+/// table; this app has no such table (and no TypeORM), so chat attachments get a
+/// purpose-built model rather than a shared one. Bytes live in MinIO — `url` is
+/// the unsigned object path, signed on read for preview.
+model SupportAttachment {
+  id        String         @id @default(uuid())
+  messageId String
+  name      String
+  mimeType  String
+  /// Bytes.
+  size      Int
+  /// Unsigned MinIO object URL. Not directly fetchable by a browser — the API
+  /// mints a short-lived signed URL per response.
+  url       String
+  createdAt DateTime       @default(now())
+  message   SupportMessage @relation(fields: [messageId], references: [id], onDelete: Cascade)
+  @@index([messageId])
   @@schema("passenger")
 }