# Task ID: 1
# Title: Build the normalization key
# Status: done
# Dependencies: None
# Priority: high
# Description: Collapse casing and surrounding whitespace so that equal contacts hash to one key.
# Details:
Add normalize_key(email, phone) that lowercases and strips both fields and
returns them as a tuple. Route every row in import_contacts.py through it before
deciding whether to insert, so that casing differences between the two source
files can no longer produce distinct keys for the same contact.

# Test Strategy:
Run the unit suite over mixed-case fixtures; every casing and padding variant of
a single contact must collapse to the same key. Verified 2026-07-09: all 15 unit
tests pass and the uppercase, title-case, and space-padded variants of one
contact now map to a single key.
