feat: add new reaction types and enforce single reaction per type

src/main/java/com/openisle/model/Reaction.java

@@ -12,7 +12,11 @@ import lombok.Setter;
 @Getter
 @Setter
 @NoArgsConstructor
-@Table(name = "reactions")
+@Table(name = "reactions",
+       uniqueConstraints = {
+           @UniqueConstraint(columnNames = {"user_id", "post_id", "type"}),
+           @UniqueConstraint(columnNames = {"user_id", "comment_id", "type"})
+       })
 public class Reaction {
     @Id
     @GeneratedValue(strategy = GenerationType.IDENTITY)

src/main/java/com/openisle/model/ReactionType.java

@@ -7,5 +7,13 @@ public enum ReactionType {
     LIKE,
     DISLIKE,
     RECOMMEND,
-    ANGRY
+    ANGRY,
+    FLUSHED,
+    STAR_STRUCK,
+    ROFL,
+    HOLDING_BACK_TEARS,
+    MIND_BLOWN,
+    POOP,
+    CLOWN,
+    SKULL
 }

src/main/java/com/openisle/service/ReactionService.java

@@ -28,6 +28,12 @@ public class ReactionService {
                 .orElseThrow(() -> new IllegalArgumentException("User not found"));
         Post post = postRepository.findById(postId)
                 .orElseThrow(() -> new IllegalArgumentException("Post not found"));
+        java.util.Optional<Reaction> existing =
+                reactionRepository.findByUserAndPostAndType(user, post, type);
+        if (existing.isPresent()) {
+            reactionRepository.delete(existing.get());
+            return null;
+        }
         Reaction reaction = new Reaction();
         reaction.setUser(user);
         reaction.setPost(post);
@@ -44,6 +50,12 @@ public class ReactionService {
                 .orElseThrow(() -> new IllegalArgumentException("User not found"));
         Comment comment = commentRepository.findById(commentId)
                 .orElseThrow(() -> new IllegalArgumentException("Comment not found"));
+        java.util.Optional<Reaction> existing =
+                reactionRepository.findByUserAndCommentAndType(user, comment, type);
+        if (existing.isPresent()) {
+            reactionRepository.delete(existing.get());
+            return null;
+        }
         Reaction reaction = new Reaction();
         reaction.setUser(user);
         reaction.setComment(comment);