[L2] Types + store layer: introduce DeploymentMode, rename clerk_id → external_id in Rust

[gbram1]

Part of an AI-generated stack — level 2 of 5.
Depends on: Level 1. Merges into: stack/pr-3/L01-db-migrations-rename-clerk-id-external-i.

Goal

Update all Rust types, metadata store implementations, and call sites so the codebase compiles against the new schema columns.

Risk

low — Mechanical rename within a bounded crate; all callers are internal and the trait API change is additive (rename only, same semantics).

Rationale

Depends on L1 so the DB columns are present when the store layer writes them. This is a pure rename refactor — no behavior change. Reviewers should check that every clerk_id reference is gone, that DeploymentMode serializes correctly to 'self_hosted'/'byoc'/'managed', and that the MetadataStore trait's get_organization_by_external_id signature change is correctly propagated to both SqliteMetadataStore and PostgresMetadataStore. Also removes the #[ignore] tag from test_topic_cache_invalidation_on_delete — reviewer should verify the FK fix in L1 actually makes this test pass.

Files (12)

• crates/streamhouse-metadata/src/types.rs
• crates/streamhouse-metadata/src/store.rs
• crates/streamhouse-metadata/src/postgres.rs
• crates/streamhouse-metadata/src/cached_store.rs
• crates/streamhouse-metadata/src/lib.rs
• crates/streamhouse-metadata/src/backup.rs
• crates/streamhouse-metadata/src/quota.rs
• crates/streamhouse-metadata/src/tenant.rs
• crates/streamhouse-metadata/tests/integration_tests.rs
• crates/streamhouse-kafka/examples/kafka_rate_limit_test.rs
• crates/streamhouse-kafka/examples/kafka_smoke_test.rs
• crates/streamhouse-kafka/src/server.rs