Fix: Remove hardcoded page limits causing parsing failures on large PDFs (>300 pages) (#14382)

### What problem does this PR solve?

Fixes #14196

## Problem

When using DeepDOC to parse large PDFs (over 1000 pages), the parser
silently truncated processing at 300 pages due to a hardcoded default
`page_to=299` in `RAGFlowPdfParser.__images__()`. This caused:

- **Errors** on pages beyond the limit
- **Poor image quality** as the parser attempted to compensate with
missing page data
- **Inconsistent chunk splitting** between full PDF imports and partial
imports

Additionally, the codebase scattered magic numbers (`299`, `600`,
`10000`, `100000`, `100000000`, `10000000000`, `10**9`) across 22 files
as sentinel values for "parse all pages", making future maintenance
error-prone.

## Root Cause

```python
# deepdoc/parser/pdf_parser.py (before)
def __images__(self, fnm, zoomin=3, page_from=0, page_to=299, callback=None):
    # Only the first 300 pages were rendered; everything beyond was silently dropped
```

While most callers in `rag/app/*.py` correctly passed `to_page=100000`,
the base class `RAGFlowPdfParser.__call__()` and `parse_into_bboxes()`
invoked `__images__` **without** forwarding `page_from`/`page_to`,
falling back to the restrictive default of 299.

## Solution

### 1. Define constants in `common/constants.py`

```python
MAXIMUM_PAGE_NUMBER = 100000                        # Used by the parsing layer
MAXIMUM_TASK_PAGE_NUMBER = MAXIMUM_PAGE_NUMBER * 1000  # Used by the task/DB layer
```

### 2. Replace all hardcoded sentinel values

| Layer | Files Changed | Old Values | New Value |
|---|---|---|---|
| **Deepdoc parsers** | `pdf_parser.py`, `mineru_parser.py`,
`docling_parser.py`, `opendataloader_parser.py`, `paddleocr_parser.py`,
`docx_parser.py` | `299`, `600`, `10**9`, `100000000` |
`MAXIMUM_PAGE_NUMBER` |
| **Chunk parsers** | `naive.py`, `book.py`, `qa.py`, `one.py`,
`manual.py`, `paper.py`, `presentation.py`, `laws.py`, `resume.py`,
`email.py`, `table.py` | `100000`, `10000`, `10000000000` |
`MAXIMUM_PAGE_NUMBER` |
| **Task/DB layer** | `db_models.py`, `task_service.py`,
`document_service.py`, `file_service.py` | `100000000` |
`MAXIMUM_TASK_PAGE_NUMBER` |

### 3. Fix `parse_into_bboxes()` missing parameters

Added `from_page`/`to_page` parameters to `parse_into_bboxes()` so that
the `rag/flow/parser/parser.py` DeepDOC path no longer falls back to the
restrictive default.

## Files Changed (22)

- `common/constants.py`
- `deepdoc/parser/pdf_parser.py`
- `deepdoc/parser/mineru_parser.py`
- `deepdoc/parser/docling_parser.py`
- `deepdoc/parser/opendataloader_parser.py`
- `deepdoc/parser/paddleocr_parser.py`
- `deepdoc/parser/docx_parser.py`
- `rag/app/naive.py`
- `rag/app/book.py`
- `rag/app/qa.py`
- `rag/app/one.py`
- `rag/app/manual.py`
- `rag/app/paper.py`
- `rag/app/presentation.py`
- `rag/app/laws.py`
- `rag/app/resume.py`
- `rag/app/email.py`
- `rag/app/table.py`
- `api/db/db_models.py`
- `api/db/services/task_service.py`
- `api/db/services/document_service.py`
- `api/db/services/file_service.py`

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)
- [x] Refactoring

---------

Signed-off-by: noob <yixiao121314@outlook.com>

common/constants.py

@@ -244,6 +244,12 @@ SVR_QUEUE_NAME = "rag_flow_svr_queue"
 SVR_CONSUMER_GROUP_NAME = "rag_flow_svr_task_broker"
 TAG_FLD = "tag_feas"
 
+# Maximum page number used as "unlimited" sentinel value.
+# Parsing layer (chunk/Pdf.__call__) uses MAXIMUM_PAGE_NUMBER.
+# Task/DB layer (Task model) uses MAXIMUM_PAGE_NUMBER * 1000 to avoid collision with user-specified page ranges.
+MAXIMUM_PAGE_NUMBER = 100000
+MAXIMUM_TASK_PAGE_NUMBER = MAXIMUM_PAGE_NUMBER * 1000
+
 
 MINERU_ENV_KEYS = ["MINERU_APISERVER", "MINERU_OUTPUT_DIR", "MINERU_BACKEND", "MINERU_SERVER_URL", "MINERU_DELETE_OUTPUT"]
 MINERU_DEFAULT_CONFIG = {