feat: add update-changelog-with-llm command to generate changelog entries from git diff using LLM

- Implemented `update-changelog-with-llm` command that analyzes staged git diff and updates CHANGELOG.md using LLM
- Added CHANGELOG.md template for new projects
- Updated init-project script to create CHANGELOG.md from template
- Added documentation for update-changelog-with-llm in library.md
- Added update-changelog-with-llm to help table in task.template
- Enhanced CHANGELOG.md to include new command in release notes

task.template

@@ -30,6 +30,7 @@ help-table() {
     rows+=("restore-dotenv-files|[path]|Extract and copy .env files from backup file.")
     rows+=("commit-with-llm||Commit with llm generated commit message.")
     rows+=("update-with-llm|[glob][prompt]|Feed files matching glob to LLM and apply changes.")
+    rows+=("update-changelog-with-llm||Update CHANGELOG.md with changes from staged git diff using LLM.")
     rows+=("log-error||Colored output for errors.")
     rows+=("log-success||Colored output for success.")
     rows+=("log-warning||Colored output for warnings.")