[feat]: simplify sglang installation with submodule, auto-sync CI, and version alignment

- Add kvcache-ai/sglang as git submodule at third_party/sglang (branch = main)
- Add top-level install.sh for one-click source installation (sglang + kt-kernel)
- Add sglang-kt as hard dependency in kt-kernel/pyproject.toml
- Add CI workflow to auto-sync sglang submodule daily and create PR
- Add CI workflow to build and publish sglang-kt to PyPI
- Integrate sglang-kt build into release-pypi.yml (version.py bump publishes both packages)
- Align sglang-kt version with ktransformers via SGLANG_KT_VERSION env var injection
- Update Dockerfile to use submodule and inject aligned version
- Update all 13 doc files, CLI hints, and i18n strings to reference new install methods

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

doc/en/kt-kernel/MiniMax-M2.1-Tutorial.md

@@ -42,17 +42,17 @@ This tutorial demonstrates how to run MiniMax-M2.1 model inference using SGLang
 
 Before starting, ensure you have:
 
-1. **SGLang installed** 
+1. **SGLang installed**
 
-    Note: Currently, please clone our custom SGLang repository:
+    Install the kvcache-ai fork of SGLang (one of):
 
     ```bash
-    git clone https://github.com/kvcache-ai/sglang.git
-    cd sglang
-    pip install -e "python[all]"
-    ```
+    # Option A: One-click install (from ktransformers root)
+    ./install.sh
 
-    You can follow [SGLang integration steps](https://docs.sglang.io/get_started/install.html)
+    # Option B: pip install
+    pip install sglang-kt
+    ```
 
 2. **KT-Kernel installed**