feat(backend): add text translation handler and update task mapping for new translation functionality

backend/internal/controllers/task/text.go

@@ -0,0 +1,45 @@
+package task
+
+import (
+	"encoding/json"
+
+	"github.com/labstack/echo/v5"
+)
+
+var validProviders = map[string]bool{
+	"google":    true,
+	"microsoft": true,
+	"deeplx":    true,
+	"deepseek":  true,
+}
+
+var validSources = map[string]bool{
+	"auto":  true,
+	"zh-CN": true,
+	"en":    true,
+	"ja":    true,
+	"ko":    true,
+}
+
+type TranslateTextRequest struct {
+	Text     string `json:"text"`
+	Source   string `json:"source"`
+	Target   string `json:"target"`
+	Provider string `json:"provider"`
+}
+
+func HandleTextTranslate(c *echo.Context) ([]byte, error) {
+	r := new(TranslateTextRequest)
+	if err := c.Bind(r); err != nil {
+		return nil, err
+	}
+	if r.Text == "" || r.Target == "" || !validProviders[r.Provider] || !validSources[r.Source] {
+		return nil, ErrInvalidRequest
+	}
+	return json.Marshal(map[string]any{
+		"text":     r.Text,
+		"source":   r.Source,
+		"target":   r.Target,
+		"provider": r.Provider,
+	})
+}