_parse_json_from_text always returns a dict (never None), so the
previous `if parsed is not None` guard was permanently true — garbled
docuvision output would return an empty skeleton instead of falling
through to the local VLM. Replace the check with a meaningful-content
test (items or merchant present). Add two tests: one that asserts the
fallthrough behavior on an empty parse, one that confirms the fast path
is taken when parsing succeeds.
Introduces a thin HTTP client for the cf-docuvision service and wires it
as a fast path in VisionLanguageOCR.extract_receipt_data(). When CF_ORCH_URL
is set, the pipeline attempts docuvision allocation via CFOrchClient before
loading the heavy local VLM; falls back gracefully if unavailable.
