### What problem does this PR solve?

Fix illegal variable name in Jinja2. #8316.

### Type of change

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

…e graph feature (#1727)

### What problem does this PR solve?

### Type of change

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

### What problem does this PR solve?

[[Critical] RagFlow has a SSTI, which can lead to Remote Code Execution
(RCE).](https://github.com/infiniflow/ragflow/security/advisories/GHSA-mrf5-7w8r-8x88#event-463508)

### Type of change

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

###Address Problem:
The original implementation used re.sub(r"(\\\"|\")", "", content) which
stripped all quotes from the processed content. While this worked for
simple Jinja2-rendered templates, it caused formatting issues when :
-Quotes were required in the final output (e.g., JSON, Python Code
strings)

###Solution:
    1. Selective JSON Serialization.
    2. Removed Global Quote Removal

### What problem does this PR solve?

This PR addresses an issue in template processing where all quotation
marks (" and \") were being removed from content, potentially corrupting
string formatting in rendered outputs. **In fact, extra quotes is
generated by json.dumps(v, ensure_ascii=False).**

### Type of change

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

### What problem does this PR solve?

#6337

### Type of change

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

### What problem does this PR solve?

### Type of change

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

### What problem does this PR solve?

#4764

### Type of change

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

### What problem does this PR solve?

Template conversion adds Jinjia2 syntax support

### Type of change

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

---------

Co-authored-by: wangrui <wangrui@haima.me>
Co-authored-by: Yingfeng <yingfeng.zhang@gmail.com>
Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

### What problem does this PR solve?

Fix errors detected by Ruff

### Type of change

- [x] Refactoring

### What problem does this PR solve?

#3585
### Type of change

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

### What problem does this PR solve?

#3560

### Type of change

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

### What problem does this PR solve?

#3556 

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)
- [x] New Feature (non-breaking change which adds functionality)