Replace SOAP DataInventory with non-SOAP solution (drop zeep)

[GClunies]

What & Why

Station.data_inventory is today the sole consumer of SOAP in this library. It calls zeep.Client(INVENTORY_WSDL_URL) against opendap.co-ops.nos.noaa.gov — a legacy endpoint the README already labels "legacy" and best-effort (README.md:79-82), with failure silently degrading to {} (station.py:63-82). Migrating this to mdapi/datagetter (or dropping the feature if no equivalent exists) lets us drop zeep entirely and remove the last SOAP surface.

This ticket is intentionally research + assess + implement in one go — not a separate spike.

Part of #89.

Acceptance Criteria

• zeep removed from pyproject.toml runtime dependencies.
• INVENTORY_WSDL_URL, _SOAP_SESSION, _SOAP_RETRY, and _build_soap_session() deleted.
• Station.get_data_inventory() / data_inventory attribute is either (a) reimplemented against mdapi or datagetter with equivalent or documented-reduced output, or (b) deprecated with a clear migration note in README/CHANGELOG.
• Cassette-backed test(s) cover the new path; the existing @pytest.mark.live SOAP test is deleted or rewritten.
• No references to soap, wsdl, zeep, or opendap.co-ops remain in noaa_coops/ source.
• Station docstring (station.py:42-45) and CHANGELOG updated.

Approach

Phase 1 — Research (time-box: ~1 day).
Investigate the three candidate paths and pick one. Post the decision in a comment on this issue before coding.

1. Derive data_inventory from mdapi fields already returned in the expand=products,deployments,bins response — check whether per-product first/last coverage dates are present.
2. Probe the datagetter with sentinel queries per product to discover coverage bounds.
3. Deprecate data_inventory entirely if no first-class equivalent exists; document the removal.

Decision criteria: coverage fidelity vs. latency cost of whatever replaces it.

Phase 2 — Implement.
Files in play:

• noaa_coops/_endpoints.py — remove INVENTORY_WSDL_URL.
• noaa_coops/_http.py:42,54-67 — remove _SOAP_RETRY, _SOAP_SESSION, _build_soap_session.
• noaa_coops/station.py:17,19,21,44-49,63-82,92-122 — drop zeep import, SOAP call path, docstring.
• pyproject.toml:28 — drop zeep>=4.2.1.
• tests/test_station.py — remove/rewrite @pytest.mark.live SOAP test.
• tests/test_http.py — remove SOAP degradation tests (or repurpose for the new code path).

Phase 3 — Verify.

• Test suite green without zeep installed in the environment.
• uv lock refresh shows no zeep chain.

Resources

• Parent epic: Epic: Full NOAA CO-OPS API coverage and remove SOAP metadata dependency #89.
• SOAP call site: noaa_coops/station.py:92-122.
• README legacy callout: README.md:79-82.
• Existing pending CHANGELOG entry about SOAP hardening becomes moot once SOAP is gone: CHANGELOG.md:12-15.