fix: Use struct field access instead of map indexing

Fix compilation errors in stats.go and ingest_opt.go:

- Change map-style indexing (stats["key"]) to struct field access (stats.FieldName)

- GetDatabaseStats() returns *metadata.DatabaseStats (struct)

- CalculateCompressionStats() returns *storage.DetailedCompressionStats (struct)

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

Author: dl-alexandre

cmd/cimis/ingest_opt.go

@@ -94,8 +94,8 @@ func cmdIngestOptimized(dataDir, appKey string, args []string) {
 	fmt.Printf("  Optimized size: %d bytes\n", optSize)
 	fmt.Printf("  Compressed: %d bytes\n", compressedSize)
 	fmt.Printf("  Overall ratio: %.2fx\n", float64(originalSize)/float64(compressedSize))
-	fmt.Printf("  Bytes per record: %.2f\n", stats["bytes_per_record"])
-	fmt.Printf("  Space savings: %.1f%%\n", stats["space_savings_pct"])
+	fmt.Printf("  Bytes per record: %.2f\n", stats.BytesPerRecord)
+	fmt.Printf("  Space savings: %.1f%%\n", stats.SpaceSavingsPct)
 	fmt.Printf("  Stored in: %s\n", chunkPath)
 
 	// Save metadata

cmd/cimis/stats.go

@@ -23,10 +23,10 @@ func cmdStats(dataDir string) {
 
 	fmt.Println("Database Statistics")
 	fmt.Println("===================")
-	fmt.Printf("Stations:           %d\n", stats["station_count"])
-	fmt.Printf("Active stations:    %d\n", stats["active_station_count"])
-	fmt.Printf("Total chunks:      %d\n", stats["chunk_count"])
-	fmt.Printf("Total rows:        %d\n", stats["total_rows"])
-	fmt.Printf("Compressed size:   %.2f MB\n", float64(stats["total_compressed_bytes"].(int64))/(1024*1024))
-	fmt.Printf("Avg compression:   %.2fx\n", stats["avg_compression_ratio"])
+	fmt.Printf("Stations:           %d\n", stats.StationCount)
+	fmt.Printf("Active stations:    %d\n", stats.ActiveStationCount)
+	fmt.Printf("Total chunks:      %d\n", stats.ChunkCount)
+	fmt.Printf("Total rows:        %d\n", stats.TotalRows)
+	fmt.Printf("Compressed size:   %.2f MB\n", float64(stats.TotalCompressedBytes)/(1024*1024))
+	fmt.Printf("Avg compression:   %.2fx\n", stats.AvgCompressionRatio)
 }