feat: Implement file upload and folder creation features by GO (#13903)

### What problem does this PR solve?

feat: Implement file upload and folder creation features

- Add file upload route in router.go
- Add file operation methods in dao/file.go
- Add util/file.go for file type detection and filename handling
- Implement file upload and folder creation endpoints in handler/file.go
- Implement file upload and folder creation logic in service/file.go
- Modify response message format in memory.go
- Add document count method in dao/document.go

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

internal/handler/memory.go

@@ -194,7 +194,7 @@ func (h *MemoryHandler) CreateMemory(c *gin.Context) {
 	// Return success response
 	c.JSON(http.StatusOK, gin.H{
 		"code":    common.CodeSuccess,
-		"message": true,
+		"message":  "success",
 		"data":    result,
 	})
 }
@@ -293,7 +293,7 @@ func (h *MemoryHandler) UpdateMemory(c *gin.Context) {
 	// Return success response
 	c.JSON(http.StatusOK, gin.H{
 		"code":    common.CodeSuccess,
-		"message": true,
+		"message":  "success",
 		"data":    result,
 	})
 }
@@ -347,7 +347,7 @@ func (h *MemoryHandler) DeleteMemory(c *gin.Context) {
 	// Return success response
 	c.JSON(http.StatusOK, gin.H{
 		"code":    common.CodeSuccess,
-		"message": true,
+		"message":  "success",
 		"data":    nil,
 	})
 }
@@ -436,7 +436,7 @@ func (h *MemoryHandler) ListMemories(c *gin.Context) {
 	// Return success response
 	c.JSON(http.StatusOK, gin.H{
 		"code":    common.CodeSuccess,
-		"message": true,
+		"message":  "success",
 		"data":    result,
 	})
 }
@@ -490,7 +490,7 @@ func (h *MemoryHandler) GetMemoryConfig(c *gin.Context) {
 	// Return success response
 	c.JSON(http.StatusOK, gin.H{
 		"code":    common.CodeSuccess,
-		"message": true,
+		"message":  "success",
 		"data":    result,
 	})
 }