feat: persist club and center likes in postgresql database

backend/src/main/java/com/rit/portal/controller/ClubController.java

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+package com.rit.portal.controller;
+
+import com.rit.portal.entity.ClubLike;
+import com.rit.portal.repository.ClubLikeRepository;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.http.ResponseEntity;
+import org.springframework.transaction.annotation.Transactional;
+import org.springframework.web.bind.annotation.*;
+
+import java.time.LocalDateTime;
+import java.util.*;
+import java.util.stream.Collectors;
+
+@RestController
+@RequestMapping("/api/clubs")
+@CrossOrigin(origins = "*")
+public class ClubController {
+
+    @Autowired
+    private ClubLikeRepository clubLikeRepository;
+
+    /**
+     * Get total count of likes for all clubs & centers
+     */
+    @GetMapping("/likes")
+    public ResponseEntity<Map<String, Long>> getAllClubLikes() {
+        List<Object[]> results = clubLikeRepository.countAllGroupedByClubId();
+        Map<String, Long> likesMap = new HashMap<>();
+        for (Object[] result : results) {
+            String clubId = (String) result[0];
+            Long count = (Long) result[1];
+            likesMap.put(clubId, count);
+        }
+        return ResponseEntity.ok(likesMap);
+    }
+
+    /**
+     * Get list of club IDs liked by a specific user or device
+     */
+    @GetMapping("/user-likes")
+    public ResponseEntity<List<String>> getUserLikedClubs(@RequestParam("userIdentifier") String userIdentifier) {
+        if (userIdentifier == null || userIdentifier.isBlank()) {
+            return ResponseEntity.ok(Collections.emptyList());
+        }
+        List<ClubLike> likes = clubLikeRepository.findByUserIdentifier(userIdentifier);
+        List<String> likedClubIds = likes.stream()
+                .map(ClubLike::getClubId)
+                .collect(Collectors.toList());
+        return ResponseEntity.ok(likedClubIds);
+    }
+
+    /**
+     * Toggle like state for a club/center by a user or device
+     */
+    @PostMapping("/{clubId}/like")
+    @Transactional
+    public ResponseEntity<Map<String, Object>> toggleClubLike(
+            @PathVariable("clubId") String clubId,
+            @RequestBody(required = false) Map<String, String> payload,
+            @RequestParam(value = "userIdentifier", required = false) String paramUserIdentifier) {
+
+        String userIdentifier = null;
+        if (payload != null && payload.containsKey("userIdentifier")) {
+            userIdentifier = payload.get("userIdentifier");
+        }
+        if ((userIdentifier == null || userIdentifier.isBlank()) && paramUserIdentifier != null) {
+            userIdentifier = paramUserIdentifier;
+        }
+        if (userIdentifier == null || userIdentifier.isBlank()) {
+            userIdentifier = "anonymous_guest";
+        }
+
+        Optional<ClubLike> existingLike = clubLikeRepository.findByClubIdAndUserIdentifier(clubId, userIdentifier);
+        boolean isNowLiked;
+
+        if (existingLike.isPresent()) {
+            clubLikeRepository.delete(existingLike.get());
+            isNowLiked = false;
+        } else {
+            ClubLike newLike = ClubLike.builder()
+                    .clubId(clubId)
+                    .userIdentifier(userIdentifier)
+                    .createdAt(LocalDateTime.now())
+                    .build();
+            clubLikeRepository.save(newLike);
+            isNowLiked = true;
+        }
+
+        long newCount = clubLikeRepository.countByClubId(clubId);
+
+        Map<String, Object> response = new HashMap<>();
+        response.put("clubId", clubId);
+        response.put("liked", isNowLiked);
+        response.put("count", newCount);
+
+        return ResponseEntity.ok(response);
+    }
+}

backend/src/main/java/com/rit/portal/entity/ClubLike.java

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+package com.rit.portal.entity;
+
+import jakarta.persistence.*;
+import lombok.*;
+import java.time.LocalDateTime;
+
+@Entity
+@Table(name = "club_likes", uniqueConstraints = {
+    @UniqueConstraint(name = "unique_club_user_like", columnNames = {"club_id", "user_identifier"})
+})
+@Getter
+@Setter
+@NoArgsConstructor
+@AllArgsConstructor
+@Builder
+public class ClubLike {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @Column(name = "club_id", nullable = false, length = 100)
+    private String clubId;
+
+    @Column(name = "user_identifier", nullable = false, length = 255)
+    private String userIdentifier;
+
+    @Column(name = "created_at")
+    @Builder.Default
+    private LocalDateTime createdAt = LocalDateTime.now();
+}

backend/src/main/java/com/rit/portal/repository/ClubLikeRepository.java

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+package com.rit.portal.repository;
+
+import com.rit.portal.entity.ClubLike;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.stereotype.Repository;
+import java.util.List;
+import java.util.Optional;
+
+@Repository
+public interface ClubLikeRepository extends JpaRepository<ClubLike, Long> {
+
+    Optional<ClubLike> findByClubIdAndUserIdentifier(String clubId, String userIdentifier);
+
+    boolean existsByClubIdAndUserIdentifier(String clubId, String userIdentifier);
+
+    long countByClubId(String clubId);
+
+    List<ClubLike> findByUserIdentifier(String userIdentifier);
+
+    @Query("SELECT c.clubId, COUNT(c) FROM ClubLike c GROUP BY c.clubId")
+    List<Object[]> countAllGroupedByClubId();
+}