feat: prefix federated resource names with gateway names

[gandhipratik203]

Summary

• Persist gateway-prefixed resource names with full upstream identity and base-slug columns, plus an idempotent migration.
• Maintain naming across registration, refresh, adoption, gateway rename, and Admin edits while preserving local names and all URIs.
• Export effective base names through both export paths, retaining federated provenance metadata without changing import restoration semantics.
• Forward the separator to gateway and migration containers and add focused regressions. The live regression is retained but has not been executed.

Scope and Limitations

References #6621; does not close it. This implements the naming behavior in AC#1 and AC#2. AC#3 remains unresolved: prefixing names cannot disambiguate URI-keyed reads. Existing server-scoped routing and ambiguity errors are unchanged. Partial issue scope still needs agreement from the issue author.

Names are not guaranteed unique: gateway slugs can collide and 255-character truncation can consume the resource portion. Export fidelity is limited by validation and column bounds; invalid or oversized bases may fall through to another candidate. Provenance fields are not restored on import. Separator changes do not rederive stored bases. Downgrade discards federated manual overrides.

Draft Status

Not ready for merge. Live gateway and PostgreSQL validation are deferred by agreement; the production-stack and live RBAC gates have not been completed.

The full unit run passed with 23,230 tests; diff coverage was 91%. Subsequent focused checks passed after type-annotation fixes. Pre-commit, Ruff, Interrogate, Pylint, package verification, and the secret scan passed. Scoped mypy and Pyrefly checks passed for the new files. Broad type checks and full Bandit still report findings outside this change.