fix(embedded): isolate cached binaries for custom URLs

[VedanthB]

Problem

Custom embedded archive URLs leave _parsed_weaviate_version empty, so distinct URLs share the same binary-cache filename. After downloading build A, requesting build B with the same cache directory silently selects A without downloading B.

Change

Use the download URL as the hash input only when no version was parsed. Explicit versions, official GitHub release URLs and resolved latest tags keep their existing cache names, preserving #1681's advancing-latest behavior. Old anonymous cache files are left untouched but no longer selected.

Add 12 regression/compatibility cases using tiny ZIP/tar archives and mocked downloads. They check selected file bytes, repeat reuse, host/path differences, legacy-cache isolation and existing official caches. Six cases fail on unchanged upstream; all 12 pass with this fix. No public API or documentation change is needed.

Validation

• Unit suite: 552 passed, 1 skipped. Serial mock suite: 70 passed.
• Ruff check/format and Flake8 pass across the workflow's source/test scope.
• Pyright 1.1.399: zero errors with the Python 3.12 environment selected explicitly.
• sdist/wheel build and twine check pass.

Live server, Docker/Pyodide and other Python/platform matrices were not run locally. The existing authlib==1.6.12 development pin conflicts with the runtime's >=1.7.1; validation used the runtime-compatible dependency without changing requirement files.

AI assistance: Codex implementation/testing and independent Codex and Claude Opus code review.

[orca-security-eu]

Orca Security Scan Summary

Status	Check	Issues by priority
Passed	Infrastructure as Code	0   0   0   0	View in Orca
Passed	SAST	0   0   0   0	View in Orca
Passed	Secrets	0   0   0   0	View in Orca
Passed	Vulnerabilities	0   0   0   0	View in Orca

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[VedanthB]

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