feat: add database constraints and indexes to PasswordHistoryEntry

- Add @column annotations with proper constraints for passwordHash and entryDate
- Set passwordHash max length to 255 characters (sufficient for bcrypt hashes)
- Mark both passwordHash and entryDate as non-nullable fields
- Add database indexes on user_id and entry_date for query performance
- Improve query performance for findByUserOrderByEntryDateDesc operations

These changes ensure data integrity at the database level and optimize
password history lookups which are performed on every password change.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: devondragon

src/main/java/com/digitalsanctuary/spring/user/persistence/model/PasswordHistoryEntry.java

@@ -2,11 +2,13 @@
 
 import java.time.LocalDateTime;
 
+import jakarta.persistence.Column;
 import jakarta.persistence.Entity;
 import jakarta.persistence.FetchType;
 import jakarta.persistence.GeneratedValue;
 import jakarta.persistence.GenerationType;
 import jakarta.persistence.Id;
+import jakarta.persistence.Index;
 import jakarta.persistence.JoinColumn;
 import jakarta.persistence.ManyToOne;
 import jakarta.persistence.Table;
@@ -19,7 +21,10 @@
  */
 @Data
 @Entity
-@Table(name = "password_history_entry")
+@Table(name = "password_history_entry", indexes = {
+    @Index(name = "idx_user_id", columnList = "user_id"),
+    @Index(name = "idx_entry_date", columnList = "entry_date")
+})
 public class PasswordHistoryEntry {
 
     /** The id. */
@@ -33,9 +38,11 @@ public class PasswordHistoryEntry {
     private User user;
 
     /** The hashed password. */
+    @Column(length = 255, nullable = false)
     private String passwordHash;
 
     /** The timestamp when the password was stored. */
+    @Column(name = "entry_date", nullable = false)
     private LocalDateTime entryDate;
 
     /**