Add plan catalog and subscription schema support, seed baselines, and real importers for core domestic subscriptions plus stable official pricing sources.
This commit also hardens the shared fetch layers so the importers can support live collection and database writes instead of relying on manual placeholders alone.
Add a top-level README plus production configuration, API, and rollout documentation. Also align deployment and runbook docs with the current runtime semantics, ports, and daily pipeline entrypoints.
