Refactor duplicated code across client and deduplication modules

[Copilot]

Pylint detected significant code duplication: 50+ line _handle_error() methods duplicated across sync/async clients, identical _should_retry() logic, and 15+ lines of duplicate-finding code repeated in two scripts.

Changes

Created client_utils.py module

• Extracted handle_error(response, endpoint) - converts HTTP errors to typed exceptions
• Extracted should_retry(status_code) - determines retriable status codes
• Removed duplicate methods from DexClient and AsyncDexClient

Added find_all_duplicates() to deduplication module

• Convenience function encapsulating email, phone, name+title, and fuzzy name matching
• Returns (matches, clusters) tuple for consistent access pattern
• Replaced duplicate logic in flag_duplicates.py and resolve_duplicates.py

Example usage:

# Before: Scripts duplicated 15+ lines of detection logic
matches = []
matches.extend(find_email_duplicates(conn))
matches.extend(find_phone_duplicates(conn))
matches.extend(find_name_and_title_duplicates(conn))
matches.extend(find_fuzzy_name_duplicates(conn, threshold=0.98))
clusters = cluster_duplicates(matches)

# After: Single function call
matches, clusters = find_all_duplicates(conn, fuzzy_threshold=0.98)

Impact

• 189 lines of duplicate code removed
• 89 lines of shared utilities added
• 22 new unit tests added for utilities (182 total tests passing)
• Remaining duplications are minimal endpoint-specific patterns in paginated GET methods

Original prompt

Find and refactor duplicated code

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