Version 1 (#160)

New front-end
Launch Chat API
Manage Sources
Enable re-embedding of all contents
Sources can be added without a notebook now
Improved settings
Enable model selector on all chats
Background processing for better experience
Dark mode
Improved Notes

Improved Docs: 
- Remove all Streamlit references from documentation
- Update deployment guides with React frontend setup
- Fix Docker environment variables format (SURREAL_URL, SURREAL_PASSWORD)
- Update docker image tag from :latest to :v1-latest
- Change navigation references (Settings → Models to just Models)
- Update development setup to include frontend npm commands
- Add MIGRATION.md guide for users upgrading from Streamlit
- Update quick-start guide with correct environment variables
- Add port 5055 documentation for API access
- Update project structure to reflect frontend/ directory
- Remove outdated source-chat documentation files

open_notebook/utils/__init__.py

@@ -0,0 +1,34 @@
+"""
+Utils package for Open Notebook.
+
+To avoid circular imports, import functions directly:
+- from open_notebook.utils.context_builder import ContextBuilder
+- from open_notebook.utils import split_text, token_count, compare_versions
+"""
+
+from .text_utils import (
+    clean_thinking_content,
+    parse_thinking_content,
+    remove_non_ascii,
+    remove_non_printable,
+    split_text,
+)
+from .token_utils import token_cost, token_count
+from .version_utils import (
+    compare_versions,
+    get_installed_version,
+    get_version_from_github,
+)
+
+__all__ = [
+    "split_text",
+    "remove_non_ascii",
+    "remove_non_printable",
+    "parse_thinking_content",
+    "clean_thinking_content",
+    "token_count",
+    "token_cost",
+    "compare_versions",
+    "get_installed_version",
+    "get_version_from_github"
+]