Docs: Update version references to v0.25.6 in READMEs and docs (#15248)

### What problem does this PR solve?

- Update version tags in README files (including translations) from
v0.25.5 to v0.25.6
- Modify Docker image references and documentation to reflect new
version
- Update version badges and image descriptions
- Maintain consistency across all language variants of README files

### Type of change

- [x] Documentation Update

sdk/python/pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "ragflow-sdk"
-version = "0.25.5"
+version = "0.25.6"
 description = "Python client sdk of [RAGFlow](https://github.com/infiniflow/ragflow). RAGFlow is an open-source RAG (Retrieval-Augmented Generation) engine based on deep document understanding."
 authors = [{ name = "Zhichang Yu", email = "yuzhichang@gmail.com" }]
 license = { text = "Apache License, Version 2.0" }

sdk/python/uv.lock

@@ -369,7 +369,7 @@ wheels = [
 
 [[package]]
 name = "ragflow-sdk"
-version = "0.25.5"
+version = "0.25.6"
 source = { virtual = "." }
 dependencies = [
     { name = "beartype" },