Feat: add OpenDataLoader PDF parser backend (#14058) (#14097)

### What problem does this PR solve?

Closes #14058.

RAGFlow supports multiple PDF parsing backends (DeepDOC, MinerU,
Docling, TCADP, PaddleOCR). This PR adds **OpenDataLoader**
([opendataloader-project/opendataloader-pdf](https://github.com/opendataloader-project/opendataloader-pdf))
as a new optional backend, giving users a deterministic, local-first
alternative with competitive table extraction accuracy.

### Type of change

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

---

### Changes

#### Backend
- `deepdoc/parser/opendataloader_parser.py` — new `OpenDataLoaderParser`
class inheriting `RAGFlowPdfParser`. Implements `check_installation()`
(guards Python package + Java 11+ runtime), `parse_pdf()` with
JSON-first extraction (heading/paragraph/table/list/image/formula) and
Markdown fallback, position-tag generation compatible with the shared
`@@page\tx0\tx1\ty0\ty1##` format, and temp-dir lifecycle with cleanup.
- `rag/app/naive.py` — new `by_opendataloader()` wrapper, registered in
`PARSERS` dict, added to `chunk_token_num=0` override list.
- `rag/flow/parser/parser.py` — `"opendataloader"` branch in the
pipeline PDF handler + check validation list.

#### Infrastructure
- `docker/entrypoint.sh` — `ensure_opendataloader()` function: opt-in
via `USE_OPENDATALOADER=true`, skips gracefully if Java is not on PATH.

#### Frontend
- `web/src/components/layout-recognize-form-field.tsx` —
`OpenDataLoader` added to `ParseDocumentType` enum and parser dropdown.
Cascades automatically to the pipeline editor's Parser component.

#### Docs
- `docs/guides/dataset/select_pdf_parser.md` — added OpenDataLoader
entry and full env-var reference.

---

### Environment variables

| Variable | Default | Description |
|---|---|---|
| `USE_OPENDATALOADER` | `false` | Set `true` to install
`opendataloader-pdf` on container startup |
| `OPENDATALOADER_VERSION` | latest | Pin the PyPI release (e.g.
`==2.2.1`) |
| `OPENDATALOADER_HYBRID` | _(unset)_ | Enable hybrid AI mode (e.g.
`docling-fast`) |
| `OPENDATALOADER_IMAGE_OUTPUT` | _(unset)_ | `off` / `embedded` /
`external` |
| `OPENDATALOADER_OUTPUT_DIR` | _(tmp)_ | Persistent output dir; temp
dir used + cleaned if unset |
| `OPENDATALOADER_DELETE_OUTPUT` | `1` | `0` to retain intermediate
files for debugging |
| `OPENDATALOADER_SANITIZE` | _(unset)_ | `1` to filter prompt-injection
patterns from output |

---

### Dependencies

- **Runtime**: `opendataloader-pdf` (PyPI, Apache 2.0) — opt-in, not
added to `pyproject.toml` core deps. Installed by
`ensure_opendataloader()` at container startup when
`USE_OPENDATALOADER=true`.
- **System**: Java 11+ on PATH (JVM is the underlying engine). The
installer skips with a warning if `java` is not found.

---

### How to test

**Standalone parser:**
```bash
source .venv/bin/activate
uv pip install opendataloader-pdf
python3 -c "
import sys; sys.path.insert(0, '.')
from deepdoc.parser.opendataloader_parser import OpenDataLoaderParser
p = OpenDataLoaderParser()
print('available:', p.check_installation())
s, t = p.parse_pdf('path/to/test.pdf', parse_method='pipeline')
print(f'sections={len(s)} tables={len(t)}')
"

```
### Benchmark vs Docling
```
file                      parser            secs  sections  tables
----------------------------------------------------------------------
text-heavy.pdf            docling           45.29       148      10
text-heavy.pdf            opendataloader     3.14       559       0
table-heavy.pdf           docling           7.05        76       3
table-heavy.pdf           opendataloader     3.71        90       0
complex.pdf               docling            42.67       114       8
complex.pdf               opendataloader     3.51       180       0
```

api/apps/llm_app.py

@@ -226,6 +226,9 @@ async def add_llm():
     elif factory == "PaddleOCR":
         api_key = apikey_json(["api_key", "provider_order"])
 
+    elif factory == "OpenDataLoader":
+        api_key = apikey_json(["api_key", "provider_order"])
+
     llm = {
         "tenant_id": current_user.id,
         "llm_factory": factory,
@@ -390,6 +393,7 @@ async def delete_factory():
 def my_llms():
     try:
         TenantLLMService.ensure_mineru_from_env(current_user.id)
+        TenantLLMService.ensure_opendataloader_from_env(current_user.id)
         include_details = request.args.get("include_details", "false").lower() == "true"
 
         if include_details: