perf(config): add Otter RAM cache layer for system configs

Introduce pkg/cache/ram on top of existing Redis/DB config reads.
GetByKey now checks local RAM before Redis. Unified invalidation clears
RAM and Redis hash fields on admin writes, with pub/sub for multi-node
RAM eviction. Add tests and wire create/update/migrator write paths.

internal/apps/admin/cache/routers.go

@@ -129,9 +129,5 @@ func saveOrUpdateConfig(ctx context.Context, key string, value string) error {
 		}
 	}
 
-	// Sync config value in Redis cache
-	if db.Redis != nil {
-		_ = db.HSetJSON(ctx, model.SystemConfigRedisHashKey, key, &sc)
-	}
-	return nil
+	return model.InvalidateSystemConfigCache(ctx, key)
 }

internal/apps/admin/system_config/routers.go

@@ -87,16 +87,16 @@ func CreateSystemConfig(c *gin.Context) {
 			return err
 		}
 
-		if err := db.HSetJSON(c.Request.Context(), model.SystemConfigRedisHashKey, req.Key, &config); err != nil {
-			return err
-		}
-
 		return nil
 	}); err != nil {
 		c.JSON(http.StatusInternalServerError, response.Err(err.Error()))
 		return
 	}
 
+	if err := model.InvalidateSystemConfigCache(c.Request.Context(), req.Key); err != nil {
+		logger.WarnF(c.Request.Context(), "清理系统配置缓存失败: %v", err)
+	}
+
 	if err := model.InvalidateVisibleSystemConfigsCache(c.Request.Context()); err != nil {
 		logger.WarnF(c.Request.Context(), "清理公共配置列表缓存失败: %v", err)
 	}
@@ -233,10 +233,6 @@ func UpdateSystemConfig(c *gin.Context) {
 			return err
 		}
 
-		if err := db.HSetJSON(c.Request.Context(), model.SystemConfigRedisHashKey, key, &config); err != nil {
-			return err
-		}
-
 		resolveStorageMigrationTasksOnDirectDriverUpdate(
 			c.Request.Context(),
 			tx,
@@ -287,6 +283,10 @@ func resolveStorageMigrationTasksOnDirectDriverUpdate(
 }
 
 func invalidateCachesAfterConfigUpdate(ctx context.Context, key string) {
+	if err := model.InvalidateSystemConfigCache(ctx, key); err != nil {
+		logger.WarnF(ctx, "清理系统配置缓存失败: %v", err)
+	}
+
 	if key == model.ConfigKeyStorageConfig {
 		upload.ResetAccessCaches()
 		upload.PublishAccessCacheInvalidation(ctx)

internal/apps/admin/system_config/routers_test.go

@@ -83,17 +83,25 @@ func TestCreateSystemConfig(t *testing.T) {
 			t.Fatalf("failed to find system config in DB: %v", err)
 		}
 
-		// Verify Redis Cache
-		var redisConfig model.SystemConfig
-		err = db.HGetJSON(context.Background(), model.SystemConfigRedisHashKey, "custom_key", &redisConfig)
-		if err != nil {
-			t.Fatalf("failed to find system config in Redis: %v", err)
+		// Verify caches are invalidated after create and repopulate on read
+		_, err = db.Redis.HGet(
+			context.Background(),
+			db.PrefixedKey(model.SystemConfigRedisHashKey),
+			"custom_key",
+		).Result()
+		if err == nil {
+			t.Fatal("expected redis cache miss immediately after create")
 		}
-		if redisConfig.Value != "custom_value" {
-			t.Errorf("CreateSystemConfig(custom_key).Value = %q, want %q", redisConfig.Value, "custom_value")
+
+		var loaded model.SystemConfig
+		if err := loaded.GetByKey(context.Background(), "custom_key"); err != nil {
+			t.Fatalf("GetByKey(custom_key) error = %v", err)
 		}
-		if redisConfig.Visibility != model.ConfigVisibilityVisible {
-			t.Errorf("CreateSystemConfig(custom_key).Visibility = %d, want %d", redisConfig.Visibility, model.ConfigVisibilityVisible)
+		if loaded.Value != "custom_value" {
+			t.Errorf("GetByKey(custom_key).Value = %q, want %q", loaded.Value, "custom_value")
+		}
+		if loaded.Visibility != model.ConfigVisibilityVisible {
+			t.Errorf("GetByKey(custom_key).Visibility = %d, want %d", loaded.Visibility, model.ConfigVisibilityVisible)
 		}
 	})
 
@@ -234,14 +242,25 @@ func TestUpdateSystemConfig(t *testing.T) {
 			t.Errorf("database values not updated: %+v", cfg)
 		}
 
-		// Verify Redis
-		var redisConfig model.SystemConfig
-		_ = db.HGetJSON(context.Background(), model.SystemConfigRedisHashKey, model.ConfigKeySiteName, &redisConfig)
-		if redisConfig.Value != "Super Site Name" {
-			t.Errorf("redis cache value not updated, got '%s'", redisConfig.Value)
+		// Verify caches are invalidated after update and repopulate on read
+		_, err := db.Redis.HGet(
+			context.Background(),
+			db.PrefixedKey(model.SystemConfigRedisHashKey),
+			model.ConfigKeySiteName,
+		).Result()
+		if err == nil {
+			t.Fatal("expected redis cache miss immediately after update")
 		}
-		if redisConfig.Visibility != model.ConfigVisibilityHidden {
-			t.Errorf("redis cache visibility = %d, want %d", redisConfig.Visibility, model.ConfigVisibilityHidden)
+
+		var loaded model.SystemConfig
+		if err := loaded.GetByKey(context.Background(), model.ConfigKeySiteName); err != nil {
+			t.Fatalf("GetByKey(site_name) error = %v", err)
+		}
+		if loaded.Value != "Super Site Name" {
+			t.Errorf("GetByKey(site_name).Value = %q, want %q", loaded.Value, "Super Site Name")
+		}
+		if loaded.Visibility != model.ConfigVisibilityHidden {
+			t.Errorf("GetByKey(site_name).Visibility = %d, want %d", loaded.Visibility, model.ConfigVisibilityHidden)
 		}
 	})