Phase 0: bootstrap Rust workspace

- Cargo workspace with 6 crates: shared, storaged, catalogd, queryd, aibridge, gateway
- shared: types (DatasetId, ObjectRef, SchemaFingerprint, DatasetManifest) + error enum
- gateway: Axum HTTP entrypoint with nested service routers + tracing
- All services expose /health stubs
- justfile with build/test/run recipes
- PRD, phase tracker, and ADR docs

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

Cargo.toml

@@ -0,0 +1,22 @@
+[workspace]
+resolver = "2"
+members = [
+    "crates/shared",
+    "crates/storaged",
+    "crates/catalogd",
+    "crates/queryd",
+    "crates/aibridge",
+    "crates/gateway",
+]
+
+[workspace.dependencies]
+tokio = { version = "1", features = ["full"] }
+axum = "0.8"
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+tracing = "0.1"
+tracing-subscriber = { version = "0.3", features = ["env-filter", "json"] }
+thiserror = "2"
+uuid = { version = "1", features = ["v4", "serde"] }
+chrono = { version = "0.4", features = ["serde"] }
+tower-http = { version = "0.6", features = ["cors", "trace"] }