docs: make cloud and settlement guidance Ledger-first

[tcconnally]

Summary

• replace the obsolete all-in-one billing bundle story with the independent Perseus / Vault / Ledger product architecture
• recast Stripe as an optional Ledger settlement adapter
• rewrite legacy launch assets as Ledger-first, runtime-neutral draft copy

Verification

• uv run --no-project --with 'pytest>=7,<10' --with 'PyYAML>=5.4,<7' python -m pytest tests/test_version_single_source.py tests/test_server.py tests/test_auth.py -q
• 108 passed
• git diff --check