fix(agent): enforce document access on POST /api/v1/agents/rerun (#15145)

## Related issues

Closes #15144

### What problem does this PR solve?

`POST /api/v1/agents/rerun` loaded a pipeline operation log by UUID via
`PipelineOperationLogService.get_documents_info` with no authorization,
then wiped chunks, reset document counters, deleted tasks, and re-queued
dataflow for the victim document.

Any authenticated user who knew a victim's pipeline log id could disrupt
parsing on documents they did not own.

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)
- [ ] New Feature (non-breaking change which adds functionality)
- [ ] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [ ] Other (please describe):

### Changes

| File | Change |
|------|--------|
| `api/apps/restful_apis/agent_api.py` | Call
`DocumentService.accessible(doc["id"], tenant_id)` before destructive
rerun operations; deny with generic `"Document not found."` |
|
`test/unit_test/api/apps/restful_apis/test_rerun_agent_authorization.py`
| Unit tests: cross-tenant log rejected, missing/unauthorized same
message, authorized rerun proceeds |

### Security notes

- **CWE-639:** Closes cross-tenant pipeline rerun / chunk wipe via
leaked log UUID.
- `tenant_id` from `@add_tenant_id_to_kwargs` is `current_user.id`;
`DocumentService.accessible` covers team-shared KBs.

### Test plan

- [ ] `pytest
test/unit_test/api/apps/restful_apis/test_rerun_agent_authorization.py`
- [ ] Manual: attacker cannot rerun victim pipeline log id

```bash
cd ragflow
uv run pytest test/unit_test/api/apps/restful_apis/test_rerun_agent_authorization.py -q
```

---------

Co-authored-by: Zhichang Yu <yuzhichang@gmail.com>

common/token_utils.py

@@ -14,6 +14,7 @@
 #  limitations under the License.
 #
 
+import hashlib
 import os
 import shutil
 import tiktoken
@@ -26,7 +27,8 @@ def _ensure_tiktoken_cache() -> str:
     os.environ["TIKTOKEN_CACHE_DIR"] = cache_dir
 
     bundled_encoding_path = get_project_base_directory("ragflow_deps", "cl100k_base.tiktoken")
-    cached_encoding_path = os.path.join(cache_dir, "9b5ad71b2ce5302211f9c61530b329a4922fc6a4")
+    encoding_url = "https://openaipublic.blob.core.windows.net/encodings/cl100k_base.tiktoken"
+    cached_encoding_path = os.path.join(cache_dir, hashlib.sha1(encoding_url.encode()).hexdigest())
 
     if os.path.exists(bundled_encoding_path) and not os.path.exists(cached_encoding_path):
         shutil.copyfile(bundled_encoding_path, cached_encoding_path)