Phase 1: storage + catalog layer

- storaged: object_store backend (LocalFileSystem), PUT/GET/DELETE/LIST endpoints
- shared: arrow_helpers with Parquet roundtrip + schema fingerprinting (2 tests)
- catalogd: in-memory registry with write-ahead manifest persistence to object storage
- catalogd: POST/GET /datasets, GET /datasets/by-name/{name}
- gateway: wires storaged + catalogd with shared object_store state
- Phase tracker updated: Phase 0 + Phase 1 gates passed

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Cargo.toml

@@ -20,3 +20,10 @@ thiserror = "2"
 uuid = { version = "1", features = ["v4", "serde"] }
 chrono = { version = "0.4", features = ["serde"] }
 tower-http = { version = "0.6", features = ["cors", "trace"] }
+object_store = { version = "0.12", features = ["aws"] }
+arrow = "55"
+parquet = { version = "55", features = ["arrow", "async"] }
+datafusion = "47"
+bytes = "1"
+futures = "0.3"
+sha2 = "0.10"