fix: match Sentry URLs by parsed hostname

[YusefSyed]

Description

Determine whether a destination is the configured Sentry endpoint by comparing
its parsed hostname with the DSN hostname instead of searching for the DSN
network-location text anywhere in the candidate string.

This prevents hostname suffixes, URL user-info, paths, and query strings from
being classified as SDK-internal. It preserves scheme-independent and raw-host
input, case-insensitive matching, IPv6 handling, and the agreed
same-host/different-port behavior. The exact contract was confirmed by the
maintainer in #7332.

Regression coverage includes the classifier and downstream trace-header
propagation decisions.

Issues

• resolves: DSN netloc substring matching misclassifies unrelated destinations as SDK-internal #7332

Validation

• uv run tox -e py3.14-common: 2,431 total cases, 173 skipped, 0 failures/errors
• uv run --group typing mypy sentry_sdk: no issues in 193 source files
• full tests/test_utils.py: 224 passed, 2 skipped
• full tests/tracing/test_misc.py: 43 passed
• full tests/integrations/stdlib/test_httplib.py: 91 passed
• uv run ruff check and uv run ruff format --check: passed
• uv run pre-commit run --all-files: passed
• git diff --check: passed

Review and tooling

AI tools assisted with repository navigation, implementation drafting, test
execution, and diff analysis. The account holder reviewed and approved the
final three-file diff and validation evidence before submission, understands
the hostname-matching contract, and accepts responsibility for the
contribution. The commands above were executed through Codex in the account
holder's local checkout; they are not presented as commands manually typed by
the account holder.

[YusefSyed]

Following up on the hostname-matching fix for #7332. The change compares parsed hostnames so suffixes, user-info, paths, and query strings do not classify a destination as SDK-internal, while retaining the existing same-host/different-port behavior. Could someone familiar with this area review the intended matching contract? Happy to make changes.