### What problem does this PR solve?

Unified API response json schema

### Type of change

- [x] Refactoring

### What problem does this PR solve?

**Added openapi specification for API routes. This creates swagger UI
similar to FastAPI to better use the API.**
Using python package `flasgger`

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

Not all routes are included since this is a work in progress.

Docs can be accessed on: `{host}:{port}/apidocs`

### What problem does this PR solve?

feat: API access key management
https://github.com/infiniflow/ragflow/issues/2846
feat: Render markdown file with remark-loader
https://github.com/infiniflow/ragflow/issues/2846

### Type of change

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

### What problem does this PR solve?

#2846

### Type of change

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

### What problem does this PR solve?


### Type of change

- [x] Refactoring

### What problem does this PR solve?

#2846

### Type of change

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

https://github.com/infiniflow/ragflow/issues/2503


### What problem does this PR solve?

_Briefly describe what this PR aims to solve. Include background context
that will help reviewers understand the purpose of the PR._

### Type of change

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

Before:

<img width="611" alt="image"
src="https://github.com/user-attachments/assets/02a3a1ee-7bfb-4fe0-9b15-11ced69cc8a3">

After:

<img width="796" alt="image"
src="https://github.com/user-attachments/assets/371136af-8d16-47aa-909b-26609d3ad60e">

<img width="557" alt="image"
src="https://github.com/user-attachments/assets/9268362f-2b6a-4ea1-9fe7-659f7292e5e1">

### What problem does this PR solve?

issue: https://github.com/infiniflow/ragflow/issues/2277

_Briefly describe what this PR aims to solve. Include background context
that will help reviewers understand the purpose of the PR._

### Type of change

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

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

### What problem does this PR solve?
#1383

### Type of change

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

### What problem does this PR solve?


### Type of change

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

### What problem does this PR solve?
fix Redis no such key #1614

### Type of change

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

---------

Signed-off-by: seaver <zhudan187@qq.com>
Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

### What problem does this PR solve?

#882 

### Type of change

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

### What problem does this PR solve?

#709 
### Type of change

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