Add SiteSchema base dataclass (#11)

[MALathon]

Summary

Create the foundational SiteSchema dataclass for site-specific PDF download configurations. This is the first step in building the schema system outlined in #10.

Changes

New Files

• fetcharoo/schemas/__init__.py - Package exports
• fetcharoo/schemas/base.py - SiteSchema dataclass implementation
• tests/test_schemas_base.py - 25 comprehensive tests

SiteSchema Features

from fetcharoo.schemas import SiteSchema

schema = SiteSchema(
    name='springer_book',
    url_pattern=r'https?://link\.springer\.com/book/.*',
    description='Springer book with chapters',
    include_patterns=['*.pdf'],
    exclude_patterns=['*bbm*', '*bfm*'],
    sort_by='numeric',
    recommended_depth=1,
    request_delay=1.0,
    test_url='https://link.springer.com/book/10.1007/978-3-031-41026-0',
    expected_min_pdfs=5
)

# URL matching
schema.matches('https://link.springer.com/book/10.1007/978-3-031-41026-0')  # True

# Get FilterConfig for integration
filter_config = schema.get_filter_config()

Attributes

Attribute	Type	Description
name	str	Unique identifier
url_pattern	str	Regex pattern for URL matching
description	str	Human-readable description
include_patterns	List[str]	Filename patterns to include
exclude_patterns	List[str]	Filename patterns to exclude
sort_by	str	Sort strategy: numeric, alpha, alpha_desc, none
sort_key	Callable	Custom sort key function
default_output_name	str	Default merged filename
recommended_depth	int	Suggested recursion depth
request_delay	float	Suggested delay between requests
test_url	str	URL for validation testing
expected_min_pdfs	int	Minimum PDFs expected in validation
version	str	Schema version string

Test Plan

• 25 tests covering all functionality
• All 269 tests pass (244 existing + 25 new)

Next Steps

This PR enables:

• Implement schema registry with auto-detection #12 - Schema registry with auto-detection
• Add built-in schemas for common sites (Springer, arXiv) #13 - Built-in schemas (Springer, arXiv)

Closes

Closes #11

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Codecov Report

❌ Patch coverage is 97.97980% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
tests/test_schemas_base.py	97.27%	4 Missing ⚠️

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