### What problem does this PR solve?

[#1987](https://github.com/infiniflow/ragflow/issues/1987)

When scanning PDF files character by character, the parser excluded
spaces if the string did not match regex. Text from [Russian
documents](https://github.com/user-attachments/files/16659706/dogovor_oferta.pdf)
needs spaces, but it does not match the regex because it uses different
alphabet. That's why PDFs were parsed incorrectly and were almost
unusable as source. Fixed that by adding Russian alphabet to regex.

There might be problems with other languages that use different
alphabets. I additionally tested [PDF in
Spanish](https://www.scusd.edu/sites/main/files/file-attachments/howtohelpyourchildsucceedinschoolspanish.pdf?1338307816)
and old [a-zA-Z...] regex parses it correctly with spaces.

### Type of change

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

### What problem does this PR solve?
#1704 

### Type of change

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

---------

Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

### What problem does this PR solve?

_fix: When parsing the bold content in PDF, the result is duplicated._

the detail: [When using OCR to recognize Chinese titles, the structure
appears to be
duplicated](https://github.com/infiniflow/ragflow/issues/1718)

### Type of change

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

### What problem does this PR solve?

#1407 #1656 

### Type of change

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

### What problem does this PR solve?

pypdf and PyPDF2 possible Infinite Loop when a comment isn't followed by
a character #59

### Type of change

- [x] Refactoring

### 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?

After checking the language of the pdf, the line will hardcode the
language into Chinese

### Type of change

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

### What problem does this PR solve?

#1407 

### Type of change

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

### What problem does this PR solve?

#1407 

### Type of change

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

### What problem does this PR solve?

Fix occasional errors in pdf table recognition

### Type of change

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

### What problem does this PR solve?

#1069 

### Type of change

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

### What problem does this PR solve?

- Update readme
- Add license

### Type of change

- [x] Documentation Update

---------

Signed-off-by: Jin Hai <haijin.chn@gmail.com>

### What problem does this PR solve?

#963 

### Type of change

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

### What problem does this PR solve?

#917 
#915

### Type of change

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

### What problem does this PR solve?

When pdfparser call `_naive_vertical_merge` method，there is a "not
concating feature " value by computing difference between `b` and `b_`'s
layoutno ,but actually is `b` and `b`. I think it's a bug, so fix it.
Please check again.

### Type of change

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

### What problem does this PR solve?

#683 

### Type of change

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

### What problem does this PR solve?
#613 

### Type of change


- [x] Other (please describe):

### What problem does this PR solve?

### Type of change

- [x] Refactoring

### What problem does this PR solve?
#451 

### Type of change

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

### What problem does this PR solve?

### Type of change

- [x] Refactoring

### What problem does this PR solve?

### Type of change

- [x] Refactoring

### What problem does this PR solve?

### Type of change

- [x] Refactoring

### What problem does this PR solve?

#445 

### Type of change

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

### What problem does this PR solve?

fix a bug comes when parse some pdf file #436 

### Type of change

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

### What problem does this PR solve?

#423 

### Type of change

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

### What problem does this PR solve?

#381 
### Type of change

- [x] Refactoring

* support snapshot download from local

* let snapshot download from local

* add use layout or not option

* trival

* fix position extraction bug

* remove delimiter for naive parser

* rename vision, add layour and tsr recognizer

* trivial fixing