feat: implement database entities, repository, controllers, and data seeder for Notes & PYQs module

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

@@ -0,0 +1,46 @@
+package com.rit.portal.entity;
+
+import jakarta.persistence.*;
+import lombok.*;
+import java.time.LocalDateTime;
+
+@Entity
+@Table(name = "notes_pyqs")
+@Getter
+@Setter
+@NoArgsConstructor
+@AllArgsConstructor
+@Builder
+public class NotePyq {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @Column(nullable = false)
+    private String title;
+
+    @Column(nullable = false)
+    private String subject;
+
+    @Column(nullable = false)
+    private String department;
+
+    @Column(nullable = false)
+    private Integer semester;
+
+    @Column(name = "file_type", nullable = false)
+    private String fileType; // 'notes', 'pyq', 'syllabus', 'assignment'
+
+    @Column(name = "download_url", nullable = false)
+    private String downloadUrl;
+
+    @Column(name = "file_size", nullable = false)
+    private String fileSize;
+
+    @Column(name = "downloads_count")
+    private Integer downloadsCount = 0;
+
+    @Column(name = "uploaded_at")
+    private LocalDateTime uploadedAt = LocalDateTime.now();
+}