Codegraph updates

update changelog.md

Features:
- Massive Objects panel to find large code entities by lines of code
- Lines of code tracking with size-based node scaling
- Draggable and collapsible UI panels
- Smart initial zoom based on node count

Changes:
- matplotlib is now optional (install with codegraph[matplotlib])
- Added code coverage with pytest-cov and Codecov integration
- Added package installation tests
- Updated README with new features and images

Release v1.1.0: Massive Objects, optional matplotlib, code coverage

* Release v1.2.0: Enhanced tooltips with links count, tabs in Unlinked panel

Added:
- Node tooltips now display "Links out" and "Links in" counts with color coding
- New "Links count" tab in the Unlinked Modules panel
- Configurable threshold filter to find nodes by connection count
- Checkboxes to filter by "links in" or "links out" criteria

Changed:
- Unlinked panel now uses tabs interface (Unlinked / Links count)

* Refactor: Extract HTML/CSS/JS templates to separate files

- Move HTML structure to templates/index.html
- Move CSS styles to templates/styles.css
- Move JavaScript code to templates/main.js
- Update vizualyzer.py to read and combine template files
- Reduce vizualyzer.py from ~2000 to ~340 lines
- Fix Connections panel positioning (now draggable like other panels)
- Update CHANGELOG.md with refactoring details

* Add display filters for nodes and links by type

- Show/hide nodes: Modules, Classes, Functions, External
- Show/hide links: Module→Module, Module→Entity, Dependencies
- Filters available in the Display panel
- Links are hidden when connected nodes are filtered out
- Update CHANGELOG with display filters feature

* Move Legend panel to the right of Controls panel

* Add CSV export option for graph data

* Add integration tests for CSV export functionality

* Add CSV export documentation to README

* Update README with new feature screenshots