feat: enhance tiered billing functionality and UI components

- Introduced new fields for billing mode and expression in the Pricing model.
- Implemented dynamic pricing breakdown component to display tiered billing details.
- Updated various components to support and render tiered billing information.
- Enhanced pricing calculation logic to accommodate dynamic pricing scenarios.
- Added tests for new billing expression functionalities and UI components.

pkg/billingexpr/compile.go

@@ -31,6 +31,12 @@ var compileEnvPrototype = map[string]interface{}{
 	"cache_read_tokens":      float64(0),
 	"cache_create_tokens":    float64(0),
 	"cache_create_1h_tokens": float64(0),
+	"img":                    float64(0),
+	"ai":                     float64(0),
+	"ao":                     float64(0),
+	"image_tokens":           float64(0),
+	"audio_input_tokens":     float64(0),
+	"audio_output_tokens":    float64(0),
 	"tier":                   func(string, float64) float64 { return 0 },
 	"header":                 func(string) string { return "" },
 	"param":                  func(string) interface{} { return nil },