Add CLAUDE.md for Claude Code guidance

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: beaufour

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+Flickr Download is a command-line utility for downloading photos from Flickr. It supports downloading individual photos, photosets, or all photos from a user, with OAuth authentication for private/restricted content.
+
+## Development Commands
+
+```bash
+# Install dependencies
+poetry install --with dev,extras
+
+# Run tests
+poetry run pytest -v
+
+# Run tests with coverage
+poetry run coverage run -m pytest
+poetry run coverage html -d coverage
+
+# Code quality checks (also run via pre-commit)
+poetry run flake8 flickr_download tests
+poetry run black --check flickr_download tests
+poetry run mypy flickr_download
+
+# Run all pre-commit hooks
+poetry run pre-commit run --all-files
+
+# Run the CLI
+poetry run flickr_download [args]
+```
+
+## Architecture
+
+### Main Package (`flickr_download/`)
+
+- **flick_download.py** - Main entry point with CLI argument parsing, core download functions (`download_set`, `download_list`, `download_photo`, `download_user`, `download_user_photos`), and OAuth handling
+- **filename_handlers.py** - Strategy pattern implementation for file naming (title, id, title_and_id, id_and_title, title_increment)
+- **utils.py** - Utility functions for caching (pickle-based), file/path sanitization, JSON serialization, and file metadata handling
+- **logging_utils.py** - `APIKeysRedacter` formatter that redacts API keys and OAuth tokens from logs
+
+### Key Patterns
+
+- **OAuth Flow**: Interactive browser-based authentication with token persistence to `~/.flickr_token`
+- **Configuration**: Both CLI arguments and YAML config file (`~/.flickr_download`) supported
+- **Caching**: Pickle-based API response caching with configurable timeout
+- **Metadata**: SQLite database for tracking downloads and enabling resumable operations
+
+## Code Quality Standards
+
+- **Black**: 100-char line length
+- **MyPy**: Strict mode enabled - full type annotations required
+- **Flake8**: 100-char line length
+- Python 3.9-3.12 supported