feat: add password management, reading persistence on feed switch, and spin animation

internal/auth/auth.go

@@ -84,6 +84,29 @@ func (s *AuthService) Authenticate(username, password string) (string, error) {
 	return tokenString, nil
 }
 
+func (s *AuthService) UpdatePassword(userID, oldPassword, newPassword string) error {
+	var currentHash string
+	err := s.db.QueryRow("SELECT password_hash FROM users WHERE id = ?", userID).Scan(&currentHash)
+	if err != nil {
+		return errors.New("user not found")
+	}
+
+	if err := bcrypt.CompareHashAndPassword([]byte(currentHash), []byte(oldPassword)); err != nil {
+		return errors.New("incorrect current password")
+	}
+
+	if len(strings.TrimSpace(newPassword)) < 6 {
+		return errors.New("new password must be at least 6 characters long")
+	}
+
+	newHash, err := bcrypt.GenerateFromPassword([]byte(newPassword), bcrypt.DefaultCost)
+	if err != nil {
+		return fmt.Errorf("failed to hash new password: %w", err)
+	}
+
+	return s.db.UpdateUserPassword(userID, string(newHash))
+}
+
 func (s *AuthService) ValidateToken(tokenString string) (*Claims, error) {
 	token, err := jwt.ParseWithClaims(tokenString, &Claims{}, func(token *jwt.Token) (interface{}, error) {
 		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {