feat(config): add sensitive word filtering system with database support

Implement sensitive word filtering feature with configurable database and Redis
support. Add security enhancements including WebSocket origin validation, improved
password strength requirements, timing attack prevention, and production JWT secret
validation. Add batch operation validation limits and optimize user blocking
queries with subqueries.

BREAKING CHANGE: Password validation now requires minimum 8 characters with uppercase,
lowercase, and digit (was 6-50 characters without complexity requirements)

internal/repository/sensitive_word_repo.go

@@ -0,0 +1,66 @@
+package repository
+
+import (
+	"context"
+
+	"carrot_bbs/internal/model"
+
+	"gorm.io/gorm"
+	"gorm.io/gorm/clause"
+)
+
+type SensitiveWordRepository interface {
+	Create(ctx context.Context, word *model.SensitiveWord) error
+	GetByWord(ctx context.Context, word string) (*model.SensitiveWord, error)
+	Update(ctx context.Context, word *model.SensitiveWord) error
+	Upsert(ctx context.Context, word *model.SensitiveWord) error
+	DeactivateByWord(ctx context.Context, word string) error
+	ListActive(ctx context.Context) ([]model.SensitiveWord, error)
+}
+
+type sensitiveWordRepository struct {
+	db *gorm.DB
+}
+
+func NewSensitiveWordRepository(db *gorm.DB) SensitiveWordRepository {
+	return &sensitiveWordRepository{db: db}
+}
+
+func (r *sensitiveWordRepository) Create(ctx context.Context, word *model.SensitiveWord) error {
+	return r.db.WithContext(ctx).Create(word).Error
+}
+
+func (r *sensitiveWordRepository) GetByWord(ctx context.Context, word string) (*model.SensitiveWord, error) {
+	var sw model.SensitiveWord
+	err := r.db.WithContext(ctx).Where("word = ?", word).First(&sw).Error
+	if err != nil {
+		return nil, err
+	}
+	return &sw, nil
+}
+
+func (r *sensitiveWordRepository) Update(ctx context.Context, word *model.SensitiveWord) error {
+	return r.db.WithContext(ctx).Save(word).Error
+}
+
+func (r *sensitiveWordRepository) Upsert(ctx context.Context, word *model.SensitiveWord) error {
+	return r.db.WithContext(ctx).Clauses(clause.OnConflict{
+		Columns: []clause.Column{{Name: "word"}},
+		DoUpdates: clause.AssignmentColumns([]string{
+			"category", "level", "is_active", "updated_by", "remark", "updated_at",
+		}),
+	}).Create(word).Error
+}
+
+func (r *sensitiveWordRepository) DeactivateByWord(ctx context.Context, word string) error {
+	return r.db.WithContext(ctx).
+		Model(&model.SensitiveWord{}).
+		Where("word = ?", word).
+		Update("is_active", false).Error
+}
+
+func (r *sensitiveWordRepository) ListActive(ctx context.Context) ([]model.SensitiveWord, error) {
+	var words []model.SensitiveWord
+	err := r.db.WithContext(ctx).Where("is_active = ?", true).Find(&words).Error
+	return words, err
+}