Add generic-web deploy recovery foundations

[cbusillo]

Summary

• add bounded existing-reservation lookup across idempotency scopes
• split read-only provider inspection from evidence materialization
• preserve legacy reconciliation snapshots while binding new snapshots to product identity
• expose the shared deploy provider adapter without route-package import cycles

Validation

• uv run --extra dev python -m unittest tests.test_generic_web_deploy tests.test_postgres_store (204 tests)
• scoped Ruff, Ruff format, and mypy
• exact stacked tree: uv run --extra dev launchplane ci unittest-shard local (2,920 targets)
• independent foundation review completed; bounded LIMIT 2 remains intentional because every multi-row result is rejected as ambiguous

Refs #2167