chore: adds pre-commit (#7242)

### What problem does this PR solve?

Sometimes after we commit the code and open the PR the CI pipeline fails
in Ruff checks. Including a pre-commit we can identify this problem
early and avoid time loss.

### 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):

.pre-commit-config.yaml

+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.6.0
+    hooks:
+      - id: check-yaml
+      - id: check-json
+      - id: end-of-file-fixer
+      - id: trailing-whitespace
+      - id: check-case-conflict
+      - id: check-merge-conflict
+      - id: mixed-line-ending
+      - id: check-symlinks
+
+  - repo: https://github.com/astral-sh/ruff-pre-commit
+    rev: v0.11.6
+    hooks:
+      - id: ruff
+        args: [ --fix ]
+      - id: ruff-format

README.md

 1. Install uv, or skip this step if it is already installed:
 
    ```bash
-   pipx install uv
+   pipx install uv pre-commit
    ```
 
 2. Clone the source code and install Python dependencies:
    git clone https://github.com/infiniflow/ragflow.git
    cd ragflow/
    uv sync --python 3.10 --all-extras # install RAGFlow dependent python modules
+   pre-commit install
    ```
 
 3. Launch the dependent services (MinIO, Elasticsearch, Redis, and MySQL) using Docker Compose:

README_id.md

 1. Instal uv, atau lewati langkah ini jika sudah terinstal:
 
    ```bash
-   pipx install uv
+   pipx install uv pre-commit
    ```
 
 2. Clone kode sumber dan instal dependensi Python:
    git clone https://github.com/infiniflow/ragflow.git
    cd ragflow/
    uv sync --python 3.10 --all-extras # install RAGFlow dependent python modules
+   pre-commit install
    ```
 
 3. Jalankan aplikasi yang diperlukan (MinIO, Elasticsearch, Redis, dan MySQL) menggunakan Docker Compose:

README_ja.md

 1. uv をインストールする。すでにインストールされている場合は、このステップをスキップしてください:
 
    ```bash
-   pipx install uv
+   pipx install uv pre-commit
    ```
 
 2. ソースコードをクローンし、Python の依存関係をインストールする:
    git clone https://github.com/infiniflow/ragflow.git
    cd ragflow/
    uv sync --python 3.10 --all-extras # install RAGFlow dependent python modules
+   pre-commit install
    ```
 
 3. Docker Compose を使用して依存サービス（MinIO、Elasticsearch、Redis、MySQL）を起動する:

README_ko.md

 1. uv를 설치하거나 이미 설치된 경우 이 단계를 건너뜁니다:
 
    ```bash
-   pipx install uv
+   pipx install uv pre-commit
    ```
 
 2. 소스 코드를 클론하고 Python 의존성을 설치합니다:
    git clone https://github.com/infiniflow/ragflow.git
    cd ragflow/
    uv sync --python 3.10 --all-extras # install RAGFlow dependent python modules
+   pre-commit install
    ```
 
 3. Docker Compose를 사용하여 의존 서비스(MinIO, Elasticsearch, Redis 및 MySQL)를 시작합니다:

README_pt_br.md

 1. Instale o `uv`, ou pule esta etapa se ele já estiver instalado:
 
    ```bash
-   pipx install uv
+   pipx install uv pre-commit
    ```
 
 2. Clone o código-fonte e instale as dependências Python:
    git clone https://github.com/infiniflow/ragflow.git
    cd ragflow/
    uv sync --python 3.10 --all-extras # instala os módulos Python dependentes do RAGFlow
+   pre-commit install
    ```
 
 3. Inicie os serviços dependentes (MinIO, Elasticsearch, Redis e MySQL) usando Docker Compose:

README_tzh.md

 1. 安裝 uv。如已安裝，可跳過此步驟：
 
    ```bash
-   pipx install uv
+   pipx install uv pre-commit
    export UV_INDEX=https://mirrors.aliyun.com/pypi/simple
    ```
 
    git clone https://github.com/infiniflow/ragflow.git
    cd ragflow/
    uv sync --python 3.10 --all-extras # install RAGFlow dependent python modules
+   pre-commit install
    ```
 
 3. 透過 Docker Compose 啟動依賴的服務（MinIO, Elasticsearch, Redis, and MySQL）：

README_zh.md

 1. 安装 uv。如已经安装，可跳过本步骤：
 
    ```bash
-   pipx install uv
+   pipx install uv pre-commit
    export UV_INDEX=https://mirrors.aliyun.com/pypi/simple
    ```
 
    git clone https://github.com/infiniflow/ragflow.git
    cd ragflow/
    uv sync --python 3.10 --all-extras # install RAGFlow dependent python modules
+   pre-commit install
    ```
 
 3. 通过 Docker Compose 启动依赖的服务（MinIO, Elasticsearch, Redis, and MySQL）：