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

internal/db/db.go

@@ -173,6 +173,15 @@ func (d *DB) CreateUser(username, passwordHash string) (*models.User, error) {
 	return u, nil
 }
 
+func (d *DB) UpdateUserPassword(userID, passwordHash string) error {
+	now := time.Now().UTC()
+	_, err := d.Exec(
+		"UPDATE users SET password_hash = ?, updated_at = ? WHERE id = ?",
+		passwordHash, now, userID,
+	)
+	return err
+}
+
 // Category operations
 func (d *DB) ListCategories() ([]models.Category, error) {
 	query := `

internal/db/db_test.go

@@ -102,4 +102,17 @@ func TestDatabaseOperations(t *testing.T) {
 	if stats.TotalFeeds != 1 || stats.TotalUnread != 1 || stats.TotalStarred != 1 || stats.TotalCategories != 1 {
 		t.Errorf("unexpected stats: %+v", stats)
 	}
+
+	// 8. Test UpdateUserPassword
+	newHash := "$2a$10$updatedhashvalue"
+	if err := database.UpdateUserPassword(u.ID, newHash); err != nil {
+		t.Fatalf("UpdateUserPassword failed: %v", err)
+	}
+	updatedUser, err := database.GetUserByUsername("admin")
+	if err != nil {
+		t.Fatalf("GetUserByUsername failed: %v", err)
+	}
+	if updatedUser.PasswordHash != newHash {
+		t.Errorf("expected hash %s, got %s", newHash, updatedUser.PasswordHash)
+	}
 }