feat: migrate DELETE /api/v1/datasets/:dataset_id/documents to Go (#15577)

## Summary

Migrate the batch document deletion endpoint from Python to Go. Two
modes supported: explicit `ids` list and `delete_all`.

## Changes

| File | Change |
|------|--------|
| `internal/dao/file2document.go` | Add `GetByDocumentID`,
`DeleteByDocumentID` |
| `internal/dao/file2document_test.go` | 5 new tests |
| `internal/dao/kb_test.go` | 2 new tests (`DecreaseDocumentNum`) |
| `internal/service/document.go` | Add `deleteDocumentFull` +
`DeleteDocuments`, refactor `DeleteDocument` |
| `internal/service/document_test.go` | 10 new tests |
| `internal/handler/document.go` | Add `documentServiceIface` +
`DeleteDocuments` handler |
| `internal/handler/document_test.go` | 7 new tests |
| `internal/router/router.go` | Register `DELETE /:dataset_id/documents`
|
| `cmd/server_main.go` | Support `RAGFLOW_DICT_PATH` env var |
| `internal/binding/rag_analyzer.go` | Use `-lpcre2-8` dynamic linking |
| `internal/dao/database.go` | Skip Error 1091/1138 during migration |
| `internal/service/llm.go` | Fix vet warning |

## Per-document cleanup

- Delete tasks from DB
- Hard-delete document + decrement KB counters
- Delete chunks from document engine (nil-guarded)
- Delete metadata from document engine (nil-guarded)
- Remove file2document mapping + file record + storage blob

## Test Results

**24 unit tests all passing** (7 DAO + 10 service + 7 handler) using
SQLite :memory: + gin.TestMode.

See [test report](docs/test_report_delete_documents.md) for manual
integration test results.

🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

internal/handler/document.go

@@ -36,9 +36,29 @@ import (
 
 var IMG_BASE64_PREFIX = "data:image/png;base64,"
 
+// documentServiceIface defines the DocumentService methods used by DocumentHandler.
+type documentServiceIface interface {
+	CreateDocument(req *service.CreateDocumentRequest) (*entity.Document, error)
+	GetDocumentByID(id string) (*service.DocumentResponse, error)
+	UpdateDocument(id string, req *service.UpdateDocumentRequest) error
+	DeleteDocument(id string) error
+	DeleteDocuments(ids []string, deleteAll bool, datasetID, userID string) (int, error)
+	ParseDocuments(datasetID, userID string, docIDs []string) ([]*service.ParseDocumentResponse, error)
+	ListDocuments(page, pageSize int) ([]*service.DocumentResponse, int64, error)
+	ListDocumentsByDatasetID(kbID string, page, pageSize int) ([]*entity.DocumentListItem, int64, error)
+	GetDocumentsByAuthorID(authorID, page, pageSize int) ([]*service.DocumentResponse, int64, error)
+	GetThumbnail(docID string) (*service.ThumbnailResponse, error)
+	GetDocumentImage(imageID string) ([]byte, error)
+	GetMetadataSummary(kbID string, docIDs []string) (map[string]interface{}, error)
+	SetDocumentMetadata(docID string, meta map[string]interface{}) error
+	DeleteDocumentMetadata(docID string, keys []string) error
+	DeleteDocumentAllMetadata(docID string) error
+	GetDocumentMetadataByID(docID string) (map[string]interface{}, error)
+}
+
 // DocumentHandler document handler
 type DocumentHandler struct {
-	documentService *service.DocumentService
+	documentService documentServiceIface
 	datasetService  *service.DatasetService
 }
 
@@ -258,6 +278,54 @@ func (h *DocumentHandler) DeleteDocument(c *gin.Context) {
 	})
 }
 
+// DeleteDocuments handles DELETE /api/v1/datasets/:dataset_id/documents
+func (h *DocumentHandler) DeleteDocuments(c *gin.Context) {
+	_, errorCode, errorMessage := GetUser(c)
+	if errorCode != common.CodeSuccess {
+		jsonError(c, errorCode, errorMessage)
+		return
+	}
+
+	datasetID := c.Param("dataset_id")
+	if datasetID == "" {
+		jsonError(c, common.CodeArgumentError, "dataset_id is required")
+		return
+	}
+
+	var req struct {
+		IDs       *[]string `json:"ids"`
+		DeleteAll bool      `json:"delete_all,omitempty"`
+	}
+	if c.Request.ContentLength > 0 {
+		if err := c.ShouldBindJSON(&req); err != nil {
+			jsonError(c, common.CodeDataError, err.Error())
+			return
+		}
+	}
+
+	var ids []string
+	if req.IDs != nil {
+		ids = *req.IDs
+	}
+	if len(ids) > 0 && req.DeleteAll {
+		jsonError(c, common.CodeArgumentError, "should not provide both ids and delete_all")
+		return
+	}
+	if len(ids) == 0 && !req.DeleteAll {
+		jsonError(c, common.CodeArgumentError, "should either provide doc ids or set delete_all(true)")
+		return
+	}
+
+	userID := c.GetString("user_id")
+	deleted, err := h.documentService.DeleteDocuments(ids, req.DeleteAll, datasetID, userID)
+	if err != nil {
+		jsonError(c, common.CodeDataError, err.Error())
+		return
+	}
+
+	jsonResponse(c, common.CodeSuccess, map[string]interface{}{"deleted": deleted}, "success")
+}
+
 // ListDocuments document list
 
 func (h *DocumentHandler) ListDocuments(c *gin.Context) {