feat(chat): schema + migration — Multi-Emoji-Reaktionen + Soft-Delete

- ChatMessageReaction + DirectMessageReaction (PK user+message, emoji-Spalte,
  1 Reaktion/User/Message = WhatsApp-Verhalten)
- deleted_at (Tombstone) auf chat_messages + direct_messages
- Realtime-Publication für beide Reaction-Tabellen
NICHT gepusht: Push triggert Auto-Migration auf Staging-DB.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/prisma/migrations/20260530_chat_reactions_and_soft_delete/migration.sql

@@ -0,0 +1,42 @@
+-- Chat-Feature: Multi-Emoji-Reaktionen + Soft-Delete (Tombstone) für Room-Chat + DMs
+-- Spiegelt die chat_message_likes-Struktur (20250712_chat_rooms_and_features),
+-- erweitert um eine emoji-Spalte. PK (user_id, message_id) = eine Reaktion pro
+-- User pro Message (neues Emoji ersetzt das alte — WhatsApp-Verhalten).
+
+-- ─── Soft-Delete: deleted_at auf beiden Message-Typen ───────────────────────
+ALTER TABLE "rebreak"."chat_messages"   ADD COLUMN "deleted_at" TIMESTAMP(3);
+ALTER TABLE "rebreak"."direct_messages" ADD COLUMN "deleted_at" TIMESTAMP(3);
+
+-- ─── Reaction-Tabelle: Room-Chat ────────────────────────────────────────────
+CREATE TABLE "rebreak"."chat_message_reactions" (
+    "user_id"    UUID NOT NULL,
+    "message_id" UUID NOT NULL,
+    "emoji"      TEXT NOT NULL,
+    "created_at" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    CONSTRAINT "chat_message_reactions_pkey" PRIMARY KEY ("user_id","message_id")
+);
+CREATE INDEX "chat_message_reactions_message_id_idx" ON "rebreak"."chat_message_reactions"("message_id");
+ALTER TABLE "rebreak"."chat_message_reactions"
+    ADD CONSTRAINT "chat_message_reactions_message_id_fkey"
+    FOREIGN KEY ("message_id") REFERENCES "rebreak"."chat_messages"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+
+-- ─── Reaction-Tabelle: Direct-Messages ──────────────────────────────────────
+CREATE TABLE "rebreak"."direct_message_reactions" (
+    "user_id"    UUID NOT NULL,
+    "message_id" UUID NOT NULL,
+    "emoji"      TEXT NOT NULL,
+    "created_at" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    CONSTRAINT "direct_message_reactions_pkey" PRIMARY KEY ("user_id","message_id")
+);
+CREATE INDEX "direct_message_reactions_message_id_idx" ON "rebreak"."direct_message_reactions"("message_id");
+ALTER TABLE "rebreak"."direct_message_reactions"
+    ADD CONSTRAINT "direct_message_reactions_message_id_fkey"
+    FOREIGN KEY ("message_id") REFERENCES "rebreak"."direct_messages"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+
+-- ─── Supabase Realtime ──────────────────────────────────────────────────────
+-- Reaction-Tabellen zur Publication (chat_messages/direct_messages sind bereits
+-- via 20260516_enable_chat_realtime drin; deren UPDATE-Events tragen das
+-- deleted_at-Tombstone). Chat-Tabellen nutzen kein RLS (Prisma via Service-Role,
+-- Scoping client-seitig via postgres_changes-Filter) — Reaction-Tabellen gleich.
+ALTER PUBLICATION supabase_realtime ADD TABLE "rebreak"."chat_message_reactions";
+ALTER PUBLICATION supabase_realtime ADD TABLE "rebreak"."direct_message_reactions";

backend/prisma/schema.prisma

@@ -381,11 +381,13 @@ model ChatMessage {
     attachmentName String?  @map("attachment_name")
     likesCount     Int      @default(0) @map("likes_count")
     createdAt      DateTime @default(now()) @map("created_at")
+    deletedAt      DateTime? @map("deleted_at")
 
-    room    ChatRoom?         @relation(fields: [roomId], references: [id], onDelete: Cascade)
+    room      ChatRoom?             @relation(fields: [roomId], references: [id], onDelete: Cascade)
-    replyTo ChatMessage?      @relation("ChatReplies", fields: [replyToId], references: [id], onDelete: SetNull)
+    replyTo   ChatMessage?          @relation("ChatReplies", fields: [replyToId], references: [id], onDelete: SetNull)
-    replies ChatMessage[]     @relation("ChatReplies")
+    replies   ChatMessage[]         @relation("ChatReplies")
-    likes   ChatMessageLike[]
+    likes     ChatMessageLike[]
+    reactions ChatMessageReaction[]
 
     @@map("chat_messages")
     @@schema("rebreak")
@@ -402,6 +404,21 @@ model ChatMessageLike {
     @@schema("rebreak")
 }
 
+model ChatMessageReaction {
+    userId    String   @map("user_id") @db.Uuid
+    messageId String   @map("message_id") @db.Uuid
+    emoji     String
+    createdAt DateTime @default(now()) @map("created_at")
+
+    message ChatMessage @relation(fields: [messageId], references: [id], onDelete: Cascade)
+
+    // Eine Reaktion pro User pro Message (neues Emoji ersetzt das alte — WhatsApp-Verhalten)
+    @@id([userId, messageId])
+    @@index([messageId])
+    @@map("chat_message_reactions")
+    @@schema("rebreak")
+}
+
 model DirectMessage {
     id             String    @id @default(uuid()) @db.Uuid
     senderId       String    @map("sender_id") @db.Uuid
@@ -414,10 +431,12 @@ model DirectMessage {
     likesCount     Int       @default(0) @map("likes_count")
     createdAt      DateTime  @default(now()) @map("created_at")
     readAt         DateTime? @map("read_at")
+    deletedAt      DateTime? @map("deleted_at")
 
-    replyTo DirectMessage?      @relation("DmReplies", fields: [replyToId], references: [id], onDelete: SetNull)
+    replyTo   DirectMessage?          @relation("DmReplies", fields: [replyToId], references: [id], onDelete: SetNull)
-    replies DirectMessage[]     @relation("DmReplies")
+    replies   DirectMessage[]         @relation("DmReplies")
-    likes   DirectMessageLike[]
+    likes     DirectMessageLike[]
+    reactions DirectMessageReaction[]
 
     @@map("direct_messages")
     @@schema("rebreak")
@@ -434,6 +453,20 @@ model DirectMessageLike {
     @@schema("rebreak")
 }
 
+model DirectMessageReaction {
+    userId    String   @map("user_id") @db.Uuid
+    messageId String   @map("message_id") @db.Uuid
+    emoji     String
+    createdAt DateTime @default(now()) @map("created_at")
+
+    message DirectMessage @relation(fields: [messageId], references: [id], onDelete: Cascade)
+
+    @@id([userId, messageId])
+    @@index([messageId])
+    @@map("direct_message_reactions")
+    @@schema("rebreak")
+}
+
 model UserFollow {
     followerId  String @map("follower_id") @db.Uuid
     followingId String @map("following_id") @db.Uuid