Match name and preferred address case-insensitively in build_log_name

[bluetoothbot]

What does this implement/fix?

build_log_name builds the log label that identifies a device session
("name @ address"). It already suppresses the prefix when the resolved
address is name.local, but the startswith check is case-sensitive
— so a name myesp with a resolved MYESP.local came out as
myesp @ MYESP.local instead of just MYESP.local.

mDNS / DNS labels are case-insensitive (RFC 6762 §16, RFC 4343), and
the rest of util.py already normalises with .lower()
(address_is_local, fixed in #1681). This brings build_log_name
into line.

Also adds the first test coverage for build_log_name. The function
was previously untested; the new parametrized cases pin the canonical
shapes (bare hostname, .local, IP-only, with/without connected_address,
multiple addresses, bracketed IPv6) plus the mixed-case rows that
exercise the fix.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Code quality improvements to existing code or addition of tests
• Other

Related issue or feature (if applicable):

• n/a

Pull request in esphome (if applicable):

• n/a

Checklist:

• The code change is tested and works locally.
• If api.proto was modified, a linked pull request has been made to esphome with the same changes. (api.proto not modified)
• Tests have been added to verify that the new code works (under tests/ folder).

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Quality Report

Changes: 2 files changed, 42 insertions(+), 3 deletions(-)

Code scan: clean

Tests: failed (FAILED)

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 (dcd9453) to head (04c59a1).

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #1693   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           26        26           
  Lines         4165      4165           
=========================================
  Hits          4165      4165           

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[codspeed-hq]

Merging this PR will not alter performance

✅ 47 untouched benchmarks

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_{Comparing bluetoothbot:koan/build-log-name-tests (04c59a1) with main (dcd9453)}