feat: remove unused address_to_bytes helper

[bluetoothbot]

What

Remove the unused address_to_bytes helper from the public API and drop its test.

Why

Issue #53 flagged that the function was unused inside the library and that its
test verified a buggy behavior: Struct(">L") packs only 4 bytes, so a 6-octet
MAC address gets silently truncated. Maintainer (@bdraco) confirmed on the
issue: "I can't seem to find any usage of it. I think we can drop it."

A grep across the local bluetooth-devices workspace (bleak-esphome,
thermopro-ble, habluetooth, dbus-fast, pySwitchbot) found no callers either —
only the bundled copy of this library itself.

How

• Drop address_to_bytes and the L_PACK = Struct(">L") constant from
  src/bluetooth_data_tools/utils.py.
• Remove the import and __all__ entry from src/bluetooth_data_tools/__init__.py.
• Remove test_address_to_bytes from tests/test_utils.py.

This is a breaking change to the public API. Anyone still relying on the
old (buggy) 4-byte output should compute the bytes themselves, e.g.
mac_to_int(addr).to_bytes(6, "big"). The commit is marked feat!: so
semantic-release will pick it up as a major bump.

Testing

• pytest tests/ --ignore=tests/benchmarks → 63 passed locally.

Closes #53

🤖 Generated with Claude Code

---

Quality Report

Changes: 3 files changed, 20 deletions(-)

Code scan: clean

Tests: failed ([Errno 13] Permission denied: 'pytest')

Branch hygiene: clean

Generated by Kōan post-mission quality pipeline

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (6c02b3b) to head (94a4b91).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #218   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            6         6           
  Lines          255       248    -7     
  Branches        38        37    -1     
=========================================
- Hits           255       248    -7     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[codspeed-hq]

Merging this PR will not alter performance

✅ 9 untouched benchmarks

---

_{Comparing koan/drop-address-to-bytes (94a4b91) with main (43b0aaa)}

[bdraco]

not marking as breaking as its likely dead in the wild and a major version bump would be worse