feat(gif-mood): hide/reveal GIFs from other participants

- Add hidden field to GifMoodUserRating (schema + migration)
- Add setGifMoodUserHidden service + action with SSE broadcast
- Current user sees Cacher/Révéler toggle in their section header
- Other users see a locked placeholder with item count when hidden

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

prisma/migrations/20260325153345_gif_mood_hidden/migration.sql

@@ -0,0 +1,21 @@
+-- RedefineTables
+PRAGMA defer_foreign_keys=ON;
+PRAGMA foreign_keys=OFF;
+CREATE TABLE "new_GifMoodUserRating" (
+    "id" TEXT NOT NULL PRIMARY KEY,
+    "sessionId" TEXT NOT NULL,
+    "userId" TEXT NOT NULL,
+    "rating" INTEGER,
+    "hidden" BOOLEAN NOT NULL DEFAULT false,
+    "createdAt" DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" DATETIME NOT NULL,
+    CONSTRAINT "GifMoodUserRating_sessionId_fkey" FOREIGN KEY ("sessionId") REFERENCES "GifMoodSession" ("id") ON DELETE CASCADE ON UPDATE CASCADE,
+    CONSTRAINT "GifMoodUserRating_userId_fkey" FOREIGN KEY ("userId") REFERENCES "User" ("id") ON DELETE CASCADE ON UPDATE CASCADE
+);
+INSERT INTO "new_GifMoodUserRating" ("createdAt", "id", "rating", "sessionId", "updatedAt", "userId") SELECT "createdAt", "id", "rating", "sessionId", "updatedAt", "userId" FROM "GifMoodUserRating";
+DROP TABLE "GifMoodUserRating";
+ALTER TABLE "new_GifMoodUserRating" RENAME TO "GifMoodUserRating";
+CREATE INDEX "GifMoodUserRating_sessionId_idx" ON "GifMoodUserRating"("sessionId");
+CREATE UNIQUE INDEX "GifMoodUserRating_sessionId_userId_key" ON "GifMoodUserRating"("sessionId", "userId");
+PRAGMA foreign_keys=ON;
+PRAGMA defer_foreign_keys=OFF;

prisma/schema.prisma

@@ -561,7 +561,8 @@ model GifMoodUserRating {
   session   GifMoodSession @relation(fields: [sessionId], references: [id], onDelete: Cascade)
   userId    String
   user      User           @relation(fields: [userId], references: [id], onDelete: Cascade)
-  rating    Int            // 1-5
+  rating    Int?           // 1-5
+  hidden    Boolean        @default(false)
   createdAt DateTime       @default(now())
   updatedAt DateTime       @updatedAt