feat(translators): add token counting support for Claude and Gemini responses

- Implemented `TokenCount` transform method across translators to calculate token usage.
- Integrated token counting logic into executor pipelines for Claude, Gemini, and CLI translators.
- Added corresponding API endpoints and handlers (`/messages/count_tokens`) for token usage retrieval.
- Enhanced translation registry to support `TokenCount` functionality alongside existing response types.

internal/translator/claude/gemini/claude_gemini_response.go

@@ -9,6 +9,7 @@ import (
 	"bufio"
 	"bytes"
 	"context"
+	"fmt"
 	"strings"
 	"time"
 
@@ -530,6 +531,10 @@ func ConvertClaudeResponseToGeminiNonStream(_ context.Context, modelName string,
 	return template
 }
 
+func GeminiTokenCount(ctx context.Context, count int64) string {
+	return fmt.Sprintf(`{"totalTokens":%d,"promptTokensDetails":[{"modality":"TEXT","tokenCount":%d}]}`, count, count)
+}
+
 // consolidateParts merges consecutive text parts and thinking parts to create a cleaner response.
 // This function processes the parts array to combine adjacent text elements and thinking elements
 // into single consolidated parts, which results in a more readable and efficient response structure.