fix(query-service): skip preloading non-json files under dashboards (S…

…igNoz#6979)

### Summary

- query-service: skip preloading non-json files under dashboards

Resolves the error log:

```
{"level":"INFO","timestamp":"2025-01-29T17:37:18.635Z","caller":"dashboards/provision.go:26","msg":"Provisioning dashboard: ","filename":".gitkeep"}
{"level":"ERROR","timestamp":"2025-01-29T17:37:18.635Z","caller":"dashboards/provision.go:38","msg":"Creating Dashboards: Error in unmarshalling json from file","filename":".gitkeep","error":"unexpected end of JSON input","stacktrace":"go.signoz.io/signoz/pkg/query-service/app/dashboards.readCurrentDir\n\t/home/sa_100696978840572610735/signoz/pkg/query-service/app/dashboards/provision.go:38\ngo.signoz.io/signoz/pkg/query-service/app/dashboards.LoadDashboardFiles\n\t/home/sa_100696978840572610735/signoz/pkg/query-service/app/dashboards/provision.go:79\ngo.signoz.io/signoz/pkg/query-service/app.NewAPIHandler\n\t/home/sa_100696978840572610735/signoz/pkg/query-service/app/http_handler.go:271\ngo.signoz.io/signoz/ee/query-service/app/api.NewAPIHandler\n\t/home/sa_100696978840572610735/signoz/ee/query-service/app/api/api.go:56\ngo.signoz.io/signoz/ee/query-service/app.NewServer\n\t/home/sa_100696978840572610735/signoz/ee/query-service/app/server.go:287\nmain.main\n\t/home/sa_100696978840572610735/signoz/ee/query-service/main.go:191\nruntime.main\n\t/home/sa_100696978840572610735/go/pkg/mod/golang.org/[email protected]/src/runtime/proc.go:271"}
```

Signed-off-by: Prashant Shahi <[email protected]>

pkg/query-service/app/dashboards/provision.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"os"
 	"path/filepath"
+	"strings"
 
 	"go.uber.org/zap"
 
@@ -23,6 +24,10 @@ func readCurrentDir(dir string, fm interfaces.FeatureLookup) error {
 
 	list, _ := file.Readdirnames(0) // 0 to read all files and folders
 	for _, filename := range list {
+		if strings.ToLower(filepath.Ext(filename)) != ".json" {
+			zap.L().Debug("Skipping non-json file", zap.String("filename", filename))
+			continue
+		}
 		zap.L().Info("Provisioning dashboard: ", zap.String("filename", filename))
 
 		// using filepath.Join for platform specific path creation