Add comprehensive Hypothesis property-based and stateful tests

- Add tests/strategies.py with 20+ reusable address generation strategies
- Add tests/conftest.py with Hypothesis profile configuration
- Add tests/test_hypothesis_properties.py with 39 property tests covering:
  - AddressFormatter idempotence and component extraction
  - ZipCodeNormalizer validation and normalization
  - AddressBuilder value preservation and fluent API
  - Address and ParseResult model invariants
  - AddressService parse consistency
- Add tests/test_hypothesis_stateful.py with 4 stateful tests:
  - AddressBuilderStateMachine for fluent API testing
  - AddressServiceStateMachine for parse/validate cycles
  - AddressParseRoundtripStateMachine for roundtrip consistency
  - ZipPlusFourBuilderStateMachine for ZIP+4 handling

Test suite expanded from 174 to 217 tests, coverage improved from 62% to 64%

Author: github-actions

tests/conftest.py

@@ -0,0 +1,14 @@
+"""Shared pytest fixtures and Hypothesis configuration.
+
+This module provides pytest fixtures and configures Hypothesis profiles
+for the test suite.
+"""
+
+from __future__ import annotations
+
+from hypothesis import Verbosity, settings
+
+# Configure Hypothesis settings for the test suite
+settings.register_profile("ci", max_examples=200, deadline=None)
+settings.register_profile("dev", max_examples=50, deadline=None)
+settings.register_profile("debug", max_examples=10, deadline=None, verbosity=Verbosity.verbose)